diff --git a/app/FormatHeuristic.hs b/app/FormatHeuristic.hs
new file mode 100644
index 0000000..cdd0a06
--- /dev/null
+++ b/app/FormatHeuristic.hs
@@ -0,0 +1,69 @@
+-- |
+-- Originally based on:
+--   https://github.com/jgm/pandoc/blob/master/src/Text/Pandoc/App/FormatHeuristics.hs
+module FormatHeuristic
+  ( formatFromFilePath
+  )
+where
+
+import Data.Char (toLower)
+import System.FilePath (takeExtension)
+import Text.Pandoc
+
+formatFromFilePath :: PandocMonad m => FilePath -> Maybe (Writer m)
+formatFromFilePath x =
+  case takeExtension (map toLower x) of
+    ".adoc" -> f "asciidoc"
+    ".asciidoc" -> f "asciidoc"
+    ".context" -> f "context"
+    ".ctx" -> f "context"
+    ".db" -> f "docbook"
+    ".doc" -> f "doc" -- so we get an "unknown reader" error
+    ".docx" -> f "docx"
+    ".dokuwiki" -> f "dokuwiki"
+    ".epub" -> f "epub"
+    ".fb2" -> f "fb2"
+    ".htm" -> f "html"
+    ".html" -> f "html"
+    ".icml" -> f "icml"
+    ".json" -> f "json"
+    ".latex" -> f "latex"
+    ".lhs" -> f "markdown+lhs"
+    ".ltx" -> f "latex"
+    ".markdown" -> f "markdown"
+    ".mkdn" -> f "markdown"
+    ".mkd" -> f "markdown"
+    ".mdwn" -> f "markdown"
+    ".mdown" -> f "markdown"
+    ".Rmd" -> f "markdown"
+    ".md" -> f "markdown"
+    ".ms" -> f "ms"
+    ".muse" -> f "muse"
+    ".native" -> f "native"
+    ".odt" -> f "odt"
+    ".opml" -> f "opml"
+    ".org" -> f "org"
+    ".pdf" -> f "pdf" -- so we get an "unknown reader" error
+    ".pptx" -> f "pptx"
+    ".roff" -> f "ms"
+    ".rst" -> f "rst"
+    ".rtf" -> f "rtf"
+    ".s5" -> f "s5"
+    ".t2t" -> f "t2t"
+    ".tei" -> f "tei"
+    ".tei.xml" -> f "tei"
+    ".tex" -> f "latex"
+    ".texi" -> f "texinfo"
+    ".texinfo" -> f "texinfo"
+    ".text" -> f "markdown"
+    ".textile" -> f "textile"
+    ".txt" -> f "markdown"
+    ".wiki" -> f "mediawiki"
+    ".xhtml" -> f "html"
+    ".ipynb" -> f "ipynb"
+    ".csv" -> f "csv"
+    ".bib" -> f "biblatex"
+    ['.', y] | y `elem` ['1' .. '9'] -> f "man"
+    _ -> Nothing
+  where
+    f k = lookup k writers
diff --git a/app/Main.hs b/app/Main.hs
index 86a0794..5149246 100644
--- a/app/Main.hs
+++ b/app/Main.hs
@@ -1,7 +1,63 @@
 module Main (main) where
 
-import           OpenAPI.Checker.Run (runChecker)
-
+import Control.Monad
+import Control.Monad.Except
+import Data.Aeson
+import qualified Data.ByteString.Lazy as BSL
+import Data.Default
+import Data.HList
+import qualified Data.Text.IO as T
+import qualified Data.Yaml as Yaml
+import FormatHeuristic
+import OpenAPI.Checker.Behavior
+import OpenAPI.Checker.Options
+import OpenAPI.Checker.Paths
+import OpenAPI.Checker.PathsPrefixTree
+import OpenAPI.Checker.Report
+import OpenAPI.Checker.Subtree
+import System.Exit
+import System.IO
+import Text.Pandoc
 
 main :: IO ()
-main = runChecker
+main = do
+  opts <- execParser optionsParserInfo
+  let parseSchema path =
+        eitherDecodeFileStrict path >>= \case
+          Left jsonErr -> do
+            Yaml.decodeFileEither path >>= \case
+              Left yamlErr -> do
+                putStrLn "Could not parse as json or yaml"
+                print jsonErr
+                print yamlErr
+                fail "Exiting"
+              Right s -> pure s
+          Right s -> pure s
+  a <- traced (step ClientSchema) <$> parseSchema (clientFile opts)
+  b <- traced (step ServerSchema) <$> parseSchema (serverFile opts)
+  let result = runCompatFormula $ checkCompatibility HNil Root (ProdCons a b)
+      runPandocIO :: PandocIO a -> ExceptT Errors IO a
+      runPandocIO x = lift (runIO x) >>= either (throwError . DocumentError) pure
+      output :: Either (PathsPrefixTree Behave AnIssue 'APILevel) () -> ExceptT Errors IO ()
+      output = case outputMode opts of
+        StdoutMode -> lift . T.putStrLn <=< runPandocIO . writeMarkdown def . generateReport
+        FileMode f -> case formatFromFilePath f of
+          Nothing -> \_ -> throwError UnknownOutputFormat
+          Just (TextWriter writer) -> lift . T.writeFile f <=< runPandocIO . writer def . generateReport
+          Just (ByteStringWriter writer) -> lift . BSL.writeFile f <=< runPandocIO . writer def . generateReport
+  either handler pure <=< runExceptT $ output result
+  case result of
+    Right () -> exitSuccess
+    Left _ -> exitWith $ ExitFailure 1
+
+data Errors
+  = DocumentError PandocError
+  | UnknownOutputFormat
+
+handler :: Errors -> IO a
+handler (DocumentError err) = do
+  T.hPutStrLn stderr (renderError err)
+  exitWith $ ExitFailure 100
+handler UnknownOutputFormat = do
+  T.hPutStrLn stderr "Could not determine output format from file extension."
+  exitWith $ ExitFailure 101
diff --git a/openapi-diff.cabal b/openapi-diff.cabal
index d05f169..fccec93 100644
--- a/openapi-diff.cabal
+++ b/openapi-diff.cabal
@@ -63,6 +63,7 @@ common common-options
                      , vector
                      , yaml
                      , hashable
+                     , pandoc-types
 
   default-extensions: ApplicativeDo
                     , BangPatterns
@@ -117,7 +118,6 @@ library
                   , OpenAPI.Checker.Paths
                   , OpenAPI.Checker.PathsPrefixTree
                   , OpenAPI.Checker.References
-                  , OpenAPI.Checker.Run
                   , OpenAPI.Checker.Subtree
                   , OpenAPI.Checker.Validate.MediaTypeObject
                   , OpenAPI.Checker.Validate.OpenApi
@@ -136,15 +136,24 @@ library
                   , OpenAPI.Checker.Common
                   , OpenAPI.Checker.Validate.SecurityScheme
                   , OpenAPI.Checker.Validate.OAuth2Flows
+                  , OpenAPI.Checker.Report
 
 executable openapi-diff
   import:              common-options
   hs-source-dirs:      app
   main-is:             Main.hs
-  build-depends:       openapi-diff
+  build-depends:
+      openapi-diff
+    , pandoc
+    , data-default
+    , bytestring
+    , yaml
+    , filepath
   ghc-options:         -threaded
                        -rtsopts
                        -with-rtsopts=-N
+  other-modules:
+    FormatHeuristic
 
 test-suite openapi-diff-test
   import:              common-options
@@ -163,6 +172,8 @@ test-suite openapi-diff-test
     , yaml
     , directory
     , filepath
+    , pandoc
+    , data-default
   ghc-options:         -threaded
                        -rtsopts
                        -with-rtsopts=-N
diff --git a/src/OpenAPI/Checker/Behavior.hs b/src/OpenAPI/Checker/Behavior.hs
index fbce0a7..1df6ba6 100644
--- a/src/OpenAPI/Checker/Behavior.hs
+++ b/src/OpenAPI/Checker/Behavior.hs
@@ -9,9 +9,9 @@ where
 
 import Data.Aeson
 import Data.Kind
-import Data.Text as T
 import Data.Typeable
 import OpenAPI.Checker.Paths
+import Text.Pandoc.Builder
 
 -- | Kind
 data BehaviorLevel
@@ -37,18 +37,20 @@ class
   Behavable (a :: BehaviorLevel) (b :: BehaviorLevel)
   where
   data Behave a b
+  describeBehaviour :: Behave a b -> Inlines
+
+type instance AdditionalQuiverConstraints Behave a b = Behavable a b
 
 class (Typeable l, Ord (Issue l), Show (Issue l)) => Issuable (l :: BehaviorLevel) where
   data Issue l :: Type
-  describeIssue :: Issue l -> Text
-  describeIssue = T.pack . show -- TODO: remove this default
+  describeIssue :: Issue l -> Blocks
   issueIsUnsupported :: Issue l -> Bool
 
 -- | A set of interactions having common unifying features
 type Behavior = Paths Behave 'APILevel
 
 instance Issuable l => ToJSON (Issue l) where
-  toJSON = toJSON . describeIssue
+  toJSON = toJSON . show
 
 data AnIssue (l :: BehaviorLevel) where
   AnIssue :: Issuable l => Issue l -> AnIssue l
diff --git a/src/OpenAPI/Checker/Paths.hs b/src/OpenAPI/Checker/Paths.hs
index b825991..66d57d3 100644
--- a/src/OpenAPI/Checker/Paths.hs
+++ b/src/OpenAPI/Checker/Paths.hs
@@ -3,6 +3,7 @@
 -- structure.
 module OpenAPI.Checker.Paths
   ( NiceQuiver
+  , AdditionalQuiverConstraints
   , Paths (..)
   , DiffPaths (..)
   , catDiffPaths
@@ -24,7 +25,10 @@ import Data.Type.Equality
 import Type.Reflection
 import Prelude hiding ((.))
 
-type NiceQuiver (q :: k -> j -> Type) (a :: k) (b :: j) = (Typeable q, Typeable a, Typeable b, Ord (q a b), Show (q a b))
+type NiceQuiver (q :: k -> j -> Type) (a :: k) (b :: j) =
+  (Typeable q, Typeable a, Typeable b, Ord (q a b), Show (q a b), AdditionalQuiverConstraints q a b)
+
+type family AdditionalQuiverConstraints (q :: k -> j -> Type) (a :: k) (b :: j) :: Constraint
 
 -- | All the possible ways to navigate between nodes in a heterogeneous tree
 -- form a quiver. The hom-sets of the free category constructed from this quiver
diff --git a/src/OpenAPI/Checker/PathsPrefixTree.hs b/src/OpenAPI/Checker/PathsPrefixTree.hs
index b13fc29..7d2e2df 100644
--- a/src/OpenAPI/Checker/PathsPrefixTree.hs
+++ b/src/OpenAPI/Checker/PathsPrefixTree.hs
@@ -1,7 +1,8 @@
 {-# LANGUAGE QuantifiedConstraints #-}
 
 module OpenAPI.Checker.PathsPrefixTree
-  ( PathsPrefixTree
+  ( PathsPrefixTree (PathsPrefixNode)
+  , AStep (..)
   , empty
   , singleton
   , fromList
@@ -24,6 +25,7 @@ import qualified Data.Text as T
 import Data.Type.Equality
 import qualified Data.TypeRepMap as TRM
 import qualified Data.Vector as V
+import qualified GHC.Exts as Exts
 import qualified GHC.Exts as TRM
 import OpenAPI.Checker.Paths
 import Type.Reflection
@@ -35,6 +37,15 @@ data PathsPrefixTree (q :: k -> k -> Type) (f :: k -> Type) (r :: k) = PathsPref
   , snocItems :: !(TRM.TypeRepMap (AStep q f r))
   }
 
+pattern PathsPrefixNode :: Ord (f r) => S.Set (f r) -> [TRM.WrapTypeable (AStep q f r)] -> PathsPrefixTree q f r
+pattern PathsPrefixNode s steps <-
+  (\(PathsPrefixTree aset m) -> (toSet aset, Exts.toList m) -> (s, steps))
+  where
+    PathsPrefixNode s steps | S.null s = PathsPrefixTree AnEmptySet (Exts.fromList steps)
+    PathsPrefixNode s steps = PathsPrefixTree (ASet s) (Exts.fromList steps)
+
+{-# COMPLETE PathsPrefixNode #-}
+
 instance (forall a. ToJSON (f a)) => ToJSON (PathsPrefixTree q f r) where
   toJSON =
     Object . getMergableObject
@@ -78,6 +89,10 @@ data ASet (a :: Type) where
   AnEmptySet :: ASet a
   ASet :: Ord a => S.Set a -> ASet a
 
+toSet :: ASet a -> S.Set a
+toSet AnEmptySet = S.empty
+toSet (ASet s) = s
+
 instance ToJSON a => ToJSON (ASet a) where
   toJSON =
     toJSON . \case
@@ -123,6 +138,7 @@ instance Semigroup (PathsPrefixTree q f r) where
   PathsPrefixTree r1 s1 <> PathsPrefixTree r2 s2 =
     PathsPrefixTree (r1 <> r2) (TRM.unionWith joinSteps s1 s2)
     where
+      joinSteps :: AStep q f r a -> AStep q f r a -> AStep q f r a
       joinSteps (AStep m1) (AStep m2) = AStep $ M.unionWith (<>) m1 m2
 
 instance Monoid (PathsPrefixTree q f r) where
@@ -135,7 +151,7 @@ fromList :: [AnItem q f r] -> PathsPrefixTree q f r
 fromList = foldMap singleton
 
 null :: PathsPrefixTree q f r -> Bool
-null (PathsPrefixTree AnEmptySet s) = TRM.size s == 0
+null (PathsPrefixTree AnEmptySet s) = all (\(TRM.WrapTypeable (AStep x)) -> all null x) (Exts.toList s)
 null _ = False
 
 foldWith
@@ -161,11 +177,11 @@ toList :: PathsPrefixTree q f r -> [AnItem q f r]
 toList t = appEndo (foldWith (\xs f -> Endo (AnItem xs f :)) t) []
 
 -- | Select a subtree by prefix
-filter :: Paths q r a -> PathsPrefixTree q f r -> PathsPrefixTree q f a
+filter :: forall q f r a. Paths q r a -> PathsPrefixTree q f r -> PathsPrefixTree q f a
 filter Root t = t
 filter (Snoc xs x) t =
   foldMap (\(AStep m) -> fold $ M.lookup x m) $
-    TRM.lookup $ snocItems $ filter xs t
+    TRM.lookup @a $ snocItems $ filter xs t
 
 -- | Embed a subtree in a larger tree with given prefix
 embed :: Paths q r a -> PathsPrefixTree q f a -> PathsPrefixTree q f r
diff --git a/src/OpenAPI/Checker/Report.hs b/src/OpenAPI/Checker/Report.hs
new file mode 100644
index 0000000..af8591f
--- /dev/null
+++ b/src/OpenAPI/Checker/Report.hs
@@ -0,0 +1,136 @@
+module OpenAPI.Checker.Report
+  ( generateReport
+  )
+where
+
+import Control.Monad.Reader
+import Control.Monad.Writer
+import Data.Foldable
+import Data.Functor
+import qualified Data.Map as M
+import Data.Maybe
+import qualified Data.Text as T
+import Data.Traversable
+import Data.TypeRepMap hiding (empty)
+import Data.Typeable
+import OpenAPI.Checker.Behavior
+import OpenAPI.Checker.Paths
+import OpenAPI.Checker.PathsPrefixTree hiding (empty)
+import qualified OpenAPI.Checker.PathsPrefixTree as P hiding (empty)
+import OpenAPI.Checker.Validate.OpenApi
+import Text.Pandoc.Builder
+
+generateReport :: Either (P.PathsPrefixTree Behave AnIssue 'APILevel) () -> Pandoc
+generateReport (Right ()) = doc $ header 1 "No breaking changes found ✨"
+generateReport (Left errs) = doc $ runReportMonad jets $ showErrs errs
+
+data ReportState = ReportState
+  { sourceJets :: [SomeReportJet Behave]
+  , headerLevel :: Int
+  }
+
+type ReportMonad = ReaderT ReportState (Writer Blocks)
+
+runReportMonad :: [SomeReportJet Behave] -> ReportMonad () -> Blocks
+runReportMonad jts =
+  execWriter
+    . flip
+      runReaderT
+      ReportState
+        { sourceJets = jts
+        , headerLevel = 1
+        }
+
+smartHeader :: Inlines -> ReportMonad ()
+smartHeader i = do
+  h <- asks headerLevel
+  tell $ header h i
+
+showErrs :: Typeable a => P.PathsPrefixTree Behave AnIssue a -> ReportMonad ()
+showErrs x@(P.PathsPrefixNode currentIssues _) = do
+  jts <- asks sourceJets
+  for_ currentIssues $ \(AnIssue i) -> tell . describeIssue $ i
+  unfoldM x (observeSomeJetShowErrs <$> jts) $ \(P.PathsPrefixNode _ subIssues) -> do
+    for_ subIssues $ \(WrapTypeable (AStep m)) ->
+      for_ (M.toList m) $ \(bhv, subErrors) -> do
+        unless (P.null subErrors) $ do
+          smartHeader $ describeBehaviour bhv
+          incrementHeaders $ showErrs subErrors
+
+unfoldM :: Monad m => a -> [a -> m a] -> (a -> m ()) -> m ()
+unfoldM a [] g = g a
+unfoldM a (f : ff) g = do
+  a' <- f a
+  unfoldM a' ff g
+
+observeSomeJetShowErrs
+  :: forall a.
+  Typeable a
+  => SomeReportJet Behave
+  -> P.PathsPrefixTree Behave AnIssue a
+  -> ReportMonad (P.PathsPrefixTree Behave AnIssue a)
+observeSomeJetShowErrs (SomeReportJet (Proxy :: Proxy a') f) x
+  | Just Refl <- eqT @a @a' = observeJetShowErrs f x
+observeSomeJetShowErrs _ x = pure x
+
+observeJetShowErrs :: ReportJet Behave a -> P.PathsPrefixTree Behave AnIssue a -> ReportMonad (P.PathsPrefixTree Behave AnIssue a)
+observeJetShowErrs jet (P.PathsPrefixNode currentIssues subIssues) = do
+  rest <- fmap (fold . join) $
+    for subIssues $ \(WrapTypeable (AStep m)) -> fmap catMaybes $
+      for (M.toList m) $ \(bhv, subErrs) ->
+        case applyReportJet jet bhv of
+          Just (Left h) -> do
+            smartHeader h
+            incrementHeaders $ showErrs subErrs
+            return Nothing
+          Just (Right jet') -> do
+            rest <- observeJetShowErrs jet' subErrs
+            return $ Just $ embed (step bhv) rest
+          Nothing -> return $ Just $ embed (step bhv) subErrs
+  return $ PathsPrefixNode currentIssues mempty <> rest
+
+-- | A "jet" is a way of simplifying expressions from "outside". The "jetted"
+-- expressions should still be completely valid and correct without the jets.
+-- Jets just make the expression more "optimized" by identifying patterns and
+-- replacing the expressions with "better" ones that have the same sematics.
+--
+-- The tem "jet" in this context was introduced in the Urbit project:
+--   https://urbit.org/docs/vere/jetting/
+--
+-- The pattern fits well for simplifying 'Behaviour' tree paths.
+class ConstructReportJet f a b c where
+  constructReportJet :: (f a b -> c) -> ReportJet f a
+
+instance (ConstructReportJet f b c d, Typeable b) => ConstructReportJet f a b (f b c -> d) where
+  constructReportJet f = ReportJet Proxy $ \x -> constructReportJet $ f x
+
+instance Typeable b => ConstructReportJet f a b Inlines where
+  constructReportJet f = TerminalJet Proxy f
+
+constructSomeReportJet :: (ConstructReportJet f a b c, Typeable a) => (f a b -> c) -> SomeReportJet f
+constructSomeReportJet = SomeReportJet Proxy . constructReportJet
+
+data ReportJet f a where
+  ReportJet :: Typeable b => Proxy b -> (f a b -> ReportJet f b) -> ReportJet f a
+  TerminalJet :: Typeable b => Proxy b -> (f a b -> Inlines) -> ReportJet f a
+
+data SomeReportJet f where
+  SomeReportJet :: Typeable a => Proxy a -> ReportJet f a -> SomeReportJet f
+
+applyReportJet :: forall f a b. Typeable b => ReportJet f a -> f a b -> Maybe (Either Inlines (ReportJet f b))
+applyReportJet (TerminalJet (Proxy :: Proxy b') f) x = eqT @b @b' <&> \Refl -> Left $ f x
+applyReportJet (ReportJet (Proxy :: Proxy b') f) x = eqT @b @b' <&> \Refl -> Right $ f x
+
+incrementHeaders :: ReportMonad x -> ReportMonad x
+incrementHeaders m = do
+  l <- asks headerLevel
+  local (\x -> x {headerLevel = l + 1}) m
+
+jets :: [SomeReportJet Behave]
+jets =
+  [ constructSomeReportJet $ \p@(AtPath _) op@(InOperation _) ->
+      strong (describeBehaviour op) <> " " <> describeBehaviour p :: Inlines
+  , constructSomeReportJet $ \InRequest InPayload PayloadSchema -> "JSON Request" :: Inlines
+  , constructSomeReportJet $ \(WithStatusCode c) ResponsePayload PayloadSchema ->
+      "JSON Response – " <> str (T.pack . show $ c) :: Inlines
+  ]
diff --git a/src/OpenAPI/Checker/Run.hs b/src/OpenAPI/Checker/Run.hs
deleted file mode 100644
index 4dc6fea..0000000
--- a/src/OpenAPI/Checker/Run.hs
+++ /dev/null
@@ -1,40 +0,0 @@
-module OpenAPI.Checker.Run (runChecker) where
-
-import Data.Aeson
-import qualified Data.ByteString.Char8 as BSC
-import Data.HList
-import qualified Data.Yaml as Yaml
-import OpenAPI.Checker.Options
-import OpenAPI.Checker.Paths
-import OpenAPI.Checker.Subtree
-import OpenAPI.Checker.Validate.OpenApi ()
-import System.Exit
-import Prelude hiding (id, (.))
-
-runChecker :: IO ()
-runChecker = do
-  opts <- execParser optionsParserInfo
-  let parseSchema path =
-        eitherDecodeFileStrict path >>= \case
-          Left jsonErr -> do
-            Yaml.decodeFileEither path >>= \case
-              Left yamlErr -> do
-                putStrLn "Could not parse as json or yaml"
-                print jsonErr
-                print yamlErr
-                fail "Exiting"
-              Right s -> pure s
-          Right s -> pure s
-  a <- traced (step ClientSchema) <$> parseSchema (clientFile opts)
-  b <- traced (step ServerSchema) <$> parseSchema (serverFile opts)
-  let report = runCompatFormula $ checkCompatibility HNil Root (ProdCons a b)
-      output = case outputMode opts of
-        StdoutMode -> BSC.putStrLn
-        FileMode f -> BSC.writeFile f
-  case report of
-    Right () -> do
-      output "No breaking changes found"
-      exitSuccess
-    Left e -> do
-      output $ Yaml.encode e
-      exitFailure
diff --git a/src/OpenAPI/Checker/Subtree.hs b/src/OpenAPI/Checker/Subtree.hs
index 22d034c..7b46b10 100644
--- a/src/OpenAPI/Checker/Subtree.hs
+++ b/src/OpenAPI/Checker/Subtree.hs
@@ -64,7 +64,7 @@ import OpenAPI.Checker.Paths
 import qualified OpenAPI.Checker.PathsPrefixTree as P
 
 class
-  NiceQuiver Step a b =>
+  (Typeable Step, Typeable a, Typeable b, Ord (Step a b), Show (Step a b)) =>
   Steppable (a :: Type) (b :: Type)
   where
   -- | How to get from an @a@ node to a @b@ node
@@ -80,6 +80,8 @@ instance Steppable TraceRoot OpenApi where
 
 type Trace = Paths Step TraceRoot
 
+type instance AdditionalQuiverConstraints Step a b = ()
+
 type Traced' a b = Env (Trace a) b
 
 type Traced a = Traced' a a
@@ -128,10 +130,12 @@ type SemanticCompatFormula = CompatFormula' Behave AnIssue 'APILevel
 
 type StructuralCompatFormula = CompatFormula' VoidQuiver Proxy ()
 
-data VoidQuiver a b where
+data VoidQuiver a b
 
 deriving stock instance Eq (VoidQuiver a b)
 
+type instance AdditionalQuiverConstraints VoidQuiver a b = ()
+
 deriving stock instance Ord (VoidQuiver a b)
 
 deriving stock instance Show (VoidQuiver a b)
@@ -297,10 +301,13 @@ memo
   -> (ProdCons (Traced a) -> CompatFormula' q f r ())
   -> (ProdCons (Traced a) -> CompatFormula' q f r ())
 memo bhv k f pc = Compose $ do
-  formula' <- memoWithKnot fixpointKnot (do
-    formula <- getCompose $ f pc
-    pure $ mapErrors (P.filter bhv) formula
-    ) (k, ask <$> pc)
+  formula' <-
+    memoWithKnot
+      fixpointKnot
+      (do
+         formula <- getCompose $ f pc
+         pure $ mapErrors (P.filter bhv) formula)
+      (k, ask <$> pc)
   pure $ mapErrors (P.embed bhv) formula'
 
 data MemoKey = SemanticMemoKey | StructuralMemoKey
diff --git a/src/OpenAPI/Checker/Validate/Header.hs b/src/OpenAPI/Checker/Validate/Header.hs
index 505fdbe..c26cc07 100644
--- a/src/OpenAPI/Checker/Validate/Header.hs
+++ b/src/OpenAPI/Checker/Validate/Header.hs
@@ -13,6 +13,7 @@ import OpenAPI.Checker.Behavior
 import OpenAPI.Checker.References ()
 import OpenAPI.Checker.Subtree
 import OpenAPI.Checker.Validate.Schema ()
+import Text.Pandoc.Builder
 
 instance Subtree Header where
   type SubtreeLevel Header = 'HeaderLevel
@@ -50,8 +51,12 @@ instance Issuable 'HeaderLevel where
     | HeaderSchemaRequired
     deriving stock (Eq, Ord, Show)
   issueIsUnsupported _ = False
+  describeIssue RequiredHeaderMissing = para "Header expected, but missing."
+  describeIssue NonEmptyHeaderRequired = para "Empty header not allowed."
+  describeIssue HeaderSchemaRequired = para "Expected header schema, but it is not present."
 
 instance Behavable 'HeaderLevel 'SchemaLevel where
   data Behave 'HeaderLevel 'SchemaLevel
     = InSchema
     deriving stock (Eq, Ord, Show)
+  describeBehaviour InSchema = "JSON Schema"
diff --git a/src/OpenAPI/Checker/Validate/Link.hs b/src/OpenAPI/Checker/Validate/Link.hs
index 4bd848f..6829f3b 100644
--- a/src/OpenAPI/Checker/Validate/Link.hs
+++ b/src/OpenAPI/Checker/Validate/Link.hs
@@ -5,6 +5,7 @@ module OpenAPI.Checker.Validate.Link () where
 import Data.OpenApi
 import OpenAPI.Checker.Behavior
 import OpenAPI.Checker.Subtree
+import Text.Pandoc.Builder
 
 instance Subtree Link where
   type SubtreeLevel Link = 'LinkLevel
@@ -18,3 +19,4 @@ instance Issuable 'LinkLevel where
     deriving (Eq, Ord, Show)
   issueIsUnsupported = \case
     LinksUnsupported -> True
+  describeIssue LinksUnsupported = para "OpenApi Diff does not currently support Link Objects."
diff --git a/src/OpenAPI/Checker/Validate/MediaTypeObject.hs b/src/OpenAPI/Checker/Validate/MediaTypeObject.hs
index ee6a951..756e3e3 100644
--- a/src/OpenAPI/Checker/Validate/MediaTypeObject.hs
+++ b/src/OpenAPI/Checker/Validate/MediaTypeObject.hs
@@ -6,19 +6,22 @@ module OpenAPI.Checker.Validate.MediaTypeObject
   )
 where
 
-import Control.Lens
+import Control.Lens hiding (para)
 import Data.Foldable as F
 import Data.HList
 import Data.HashMap.Strict.InsOrd as IOHM
 import Data.Map.Strict as M
 import Data.OpenApi
+import Data.String
 import Data.Text (Text)
+import qualified Data.Text as T
 import Network.HTTP.Media (MediaType, mainType, subType)
 import OpenAPI.Checker.Behavior
 import OpenAPI.Checker.Subtree
 import OpenAPI.Checker.Validate.Header ()
 import OpenAPI.Checker.Validate.Products
 import OpenAPI.Checker.Validate.Schema ()
+import Text.Pandoc.Builder
 
 tracedSchema :: Traced MediaTypeObject -> Maybe (Traced (Referenced Schema))
 tracedSchema mto = _mediaTypeObjectSchema (extract mto) <&> traced (ask mto >>> step MediaTypeSchema)
@@ -31,9 +34,7 @@ tracedEncoding mto =
 
 instance Issuable 'PayloadLevel where
   data Issue 'PayloadLevel
-    = PayloadMediaTypeNotFound
-    | MediaEncodingIncompat
-    | MediaTypeSchemaRequired
+    = MediaTypeSchemaRequired
     | MediaEncodingMissing Text
     | EncodingNotSupported
     deriving (Eq, Ord, Show)
@@ -41,10 +42,15 @@ instance Issuable 'PayloadLevel where
     EncodingNotSupported -> True
     _ -> False
 
+  describeIssue MediaTypeSchemaRequired = para "Media type expected, but was not specified."
+  describeIssue (MediaEncodingMissing enc) = para $ "Media encoding " <> str enc <> " expected, but was not specified."
+  describeIssue EncodingNotSupported = para "OpenApi Diff does not currently support media encodings other than JSON."
+
 instance Behavable 'PayloadLevel 'SchemaLevel where
   data Behave 'PayloadLevel 'SchemaLevel
     = PayloadSchema
     deriving (Eq, Ord, Show)
+  describeBehaviour PayloadSchema = "JSON Schema"
 
 instance Subtree MediaTypeObject where
   type SubtreeLevel MediaTypeObject = 'PayloadLevel
@@ -136,15 +142,22 @@ instance Behavable 'OperationLevel 'ResponseLevel where
   data Behave 'OperationLevel 'ResponseLevel
     = WithStatusCode HttpStatusCode
     deriving stock (Eq, Ord, Show)
+  describeBehaviour (WithStatusCode c) = "Response code " <> (fromString . show $ c)
 
 instance Issuable 'OperationLevel where
   data Issue 'OperationLevel
     = ResponseCodeNotFound HttpStatusCode
-    | CallbacksNotSupported
     | ParamNotMatched Text
     | PathFragmentNotMatched Int
     | NoRequestBody
     deriving stock (Eq, Ord, Show)
   issueIsUnsupported = \case
-    CallbacksNotSupported -> True
     _ -> False
+  describeIssue (ResponseCodeNotFound c) =
+    para $ "Reponse code " <> (str . T.pack . show $ c) <> " is not supported."
+  describeIssue (ParamNotMatched param) =
+    para $ "Parameter " <> str param <> " is not supported."
+  describeIssue (PathFragmentNotMatched i) =
+    -- TODO: Indices are meaningless in this context. Replace with a better error.
+    para $ "Path fragment " <> (str . T.pack . show $ i) <> " not matched."
+  describeIssue NoRequestBody = para "Request body not specified."
diff --git a/src/OpenAPI/Checker/Validate/OAuth2Flows.hs b/src/OpenAPI/Checker/Validate/OAuth2Flows.hs
index 32766c1..121a466 100644
--- a/src/OpenAPI/Checker/Validate/OAuth2Flows.hs
+++ b/src/OpenAPI/Checker/Validate/OAuth2Flows.hs
@@ -9,6 +9,7 @@ where
 
 import Control.Monad
 import Data.Function
+import Data.Functor
 import qualified Data.HashMap.Strict.InsOrd as IOHM
 import Data.OpenApi
 import Data.Proxy
@@ -18,6 +19,7 @@ import Data.Text (Text)
 import OpenAPI.Checker.Behavior
 import OpenAPI.Checker.Orphans ()
 import OpenAPI.Checker.Subtree
+import Text.Pandoc.Builder
 
 instance Subtree OAuth2Flows where
   type CheckEnv OAuth2Flows = '[]
@@ -102,6 +104,8 @@ instance Issuable 'SecurityRequirementLevel where
     | UndefinedSecurityScheme Text
     deriving stock (Eq, Ord, Show)
   issueIsUnsupported _ = False
+  describeIssue SecurityRequirementNotMet = para "Security scheme was not met."
+  describeIssue (UndefinedSecurityScheme k) = para $ "Security scheme " <> code k <> " is not defined."
 
 instance Issuable 'SecuritySchemeLevel where
   data Issue 'SecuritySchemeLevel
@@ -125,8 +129,29 @@ instance Issuable 'SecuritySchemeLevel where
     | ScopeNotDefined Text
     deriving stock (Eq, Ord, Show)
   issueIsUnsupported _ = False
+  describeIssue RefreshUrlsDontMatch = para "Refresh URLs differ."
+  describeIssue (HttpSchemeTypesDontMatch _ _) = para "HTTP scheme types don't match."
+  describeIssue (ApiKeyParamsDontMatch _ _) = para "API Key parameters don't match."
+  describeIssue (OpenIdConnectUrlsDontMatch _ _) = para "OpenaId Connect URLs don't match."
+  describeIssue (CustomHttpSchemesDontMatch e a) =
+    para $ "Expected HTTP scheme " <> code e <> " but got " <> code a <> "."
+  describeIssue ConsumerDoesNotSupportImplicitFlow = para "Implicit flow not supported."
+  describeIssue ConsumerDoesNotSupportPasswordFlow = para "Password flow not supported."
+  describeIssue ConsumerDoesNotSupportClientCridentialsFlow = para "Client Cridentials flow not supported."
+  describeIssue ConsumerDoesNotSupportAuthorizationCodeFlow = para "Authorization Code flow not supported."
+  describeIssue SecuritySchemeNotMatched = para "Security scheme not met."
+  describeIssue OAuth2ImplicitFlowNotEqual = para "Implicit Flows don't match."
+  describeIssue OAuth2PasswordFlowNotEqual = para "Password Flows don't match."
+  describeIssue OAuth2ClientCredentialsFlowNotEqual = para "Client Cridentials Flows don't match."
+  describeIssue OAuth2AuthorizationCodeFlowNotEqual = para "Authorization Code Flows don't match."
+  describeIssue (ScopesMissing ss) =
+    para "Scopes missing:" <> bulletList (S.toList ss <&> codeBlock)
+  describeIssue DifferentSecuritySchemes = para "Completely different security scheme types."
+  describeIssue CanNotHaveScopes = para "The specified security scheme can not have scopes."
+  describeIssue (ScopeNotDefined k) = para $ "Scope with key " <> code k <> " is not defined."
 
 instance Behavable 'SecurityRequirementLevel 'SecuritySchemeLevel where
   data Behave 'SecurityRequirementLevel 'SecuritySchemeLevel
     = SecuritySchemeStep Text
     deriving stock (Eq, Ord, Show)
+  describeBehaviour (SecuritySchemeStep s) = text s
diff --git a/src/OpenAPI/Checker/Validate/OpenApi.hs b/src/OpenAPI/Checker/Validate/OpenApi.hs
index 4e654f4..dc691ed 100644
--- a/src/OpenAPI/Checker/Validate/OpenApi.hs
+++ b/src/OpenAPI/Checker/Validate/OpenApi.hs
@@ -3,7 +3,7 @@
 {-# OPTIONS_GHC -fconstraint-solver-iterations=0 #-}
 
 module OpenAPI.Checker.Validate.OpenApi
-  (
+  ( Behave (..)
   )
 where
 
diff --git a/src/OpenAPI/Checker/Validate/Operation.hs b/src/OpenAPI/Checker/Validate/Operation.hs
index 4641d3d..26a8ff6 100644
--- a/src/OpenAPI/Checker/Validate/Operation.hs
+++ b/src/OpenAPI/Checker/Validate/Operation.hs
@@ -13,6 +13,7 @@ module OpenAPI.Checker.Validate.Operation
   , ProcessedPathItems (..)
   , processPathItems
   , Step (..)
+  , Behave (..)
   )
 where
 
@@ -27,6 +28,7 @@ import qualified Data.List as L
 import Data.Map.Strict as M
 import Data.Maybe
 import Data.OpenApi
+import Data.String
 import Data.Text (Text)
 import qualified Data.Text as T
 import OpenAPI.Checker.Behavior
@@ -36,11 +38,12 @@ import OpenAPI.Checker.Validate.MediaTypeObject
 import OpenAPI.Checker.Validate.OAuth2Flows
 import OpenAPI.Checker.Validate.PathFragment
 import OpenAPI.Checker.Validate.Products
-import OpenAPI.Checker.Validate.RequestBody ()
-import OpenAPI.Checker.Validate.Responses ()
+import OpenAPI.Checker.Validate.RequestBody
+import OpenAPI.Checker.Validate.Responses
 import OpenAPI.Checker.Validate.SecurityRequirement ()
 import OpenAPI.Checker.Validate.Server ()
 import OpenAPI.Checker.Validate.Sums
+import Text.Pandoc.Builder
 
 data MatchedOperation = MatchedOperation
   { operation :: !Operation
@@ -95,18 +98,24 @@ getServers env oper =
 instance Behavable 'OperationLevel 'PathFragmentLevel where
   data Behave 'OperationLevel 'PathFragmentLevel
     = InParam Text
-    | InFragment Int
+    | InFragment (PathFragment Text)
     deriving stock (Eq, Ord, Show)
+  describeBehaviour (InParam p) = "Parameter " <> text p
+  describeBehaviour (InFragment (StaticPath p)) = "Static fragment " <> code p
+  describeBehaviour (InFragment (DynamicPath p)) = "Dynamic fragment " <> code p
 
 instance Behavable 'OperationLevel 'RequestLevel where
   data Behave 'OperationLevel 'RequestLevel
     = InRequest
     deriving stock (Eq, Ord, Show)
+  describeBehaviour InRequest = "Request"
 
 instance Behavable 'OperationLevel 'SecurityRequirementLevel where
   data Behave 'OperationLevel 'SecurityRequirementLevel
     = SecurityRequirementStep Int
     deriving stock (Eq, Ord, Show)
+  describeBehaviour (SecurityRequirementStep i) =
+    "Security requirement " <> (text . T.pack . show $ i)
 
 instance Subtree MatchedOperation where
   type SubtreeLevel MatchedOperation = 'OperationLevel
@@ -202,7 +211,8 @@ instance Subtree MatchedOperation where
             fragments = getFragments <$> pathParams <*> prodCons
             getFragments params mop = getPathFragments (extract mop) params
             -- Feed path parameters to the fragments getter
-            check idx frags = checkCompatibility @PathFragmentParam env (beh >>> step (InFragment idx)) frags
+            check _ frags@(ProdCons (Traced _ p) _) =
+              checkCompatibility @PathFragmentParam env (beh >>> step (InFragment $ _paramName . extract <$> p)) frags
             elements =
               fragments <&> \frags -> M.fromList $
                 zip [0 :: Int ..] $ do
@@ -348,12 +358,16 @@ instance Issuable 'APILevel where
     -- When several paths match given but all checks failed
     deriving stock (Eq, Ord, Show)
   issueIsUnsupported _ = False
+  describeIssue (NoPathsMatched p) = para $ "The path " <> (code . T.pack) p <> " did not match anything."
+  describeIssue (AllPathsFailed p) = para $ "The path " <> (code . T.pack) p <> " did not match anything."
 
 instance Behavable 'APILevel 'PathLevel where
   data Behave 'APILevel 'PathLevel
-    = AtPath (ProdCons FilePath) -- TODO: why are there two?
+    = AtPath FilePath
     deriving stock (Eq, Ord, Show)
 
+  describeBehaviour (AtPath p) = str (T.pack p)
+
 instance Subtree ProcessedPathItems where
   type SubtreeLevel ProcessedPathItems = 'APILevel
   type
@@ -376,15 +390,16 @@ instance Subtree ProcessedPathItems where
     -- one way
     for_ (unProcessedPathItems . extract $ p) $ \prodItem -> do
       let prodPath = path prodItem
+          beh' = beh >>> step (AtPath prodPath)
           matchedItems = do
             consItem <- unProcessedPathItems . extract $ c
             F.toList $ matchingPathItems $ ProdCons prodItem consItem
       case matchedItems of
         [] -> issueAt beh $ NoPathsMatched prodPath
-        [match] -> checkCompatibility env (beh >>> step (AtPath $ matchedPath <$> match)) (retraced <$> pc <*> match)
+        [match] -> checkCompatibility env beh' (retraced <$> pc <*> match)
         matches -> anyOfAt beh (AllPathsFailed prodPath) $ do
           match <- matches
-          pure $ checkCompatibility env (beh >>> step (AtPath $ matchedPath <$> match)) (retraced <$> pc <*> match)
+          pure $ checkCompatibility env beh' (retraced <$> pc <*> match)
     where
       retraced pc mpi = traced (ask pc >>> step (MatchedPathStep $ matchedPath mpi)) mpi
 
@@ -429,7 +444,6 @@ tracedMatchedPathItemParameters mpi =
   | (i, x) <- L.zip [0 ..] $ _pathItemParameters . pathItem $ extract mpi
   ]
 
--- TODO: simplify?
 tracedFragments :: Traced MatchedPathItem -> [Env (Trace PathFragmentParam) (PathFragment Text)]
 tracedFragments mpi =
   [ env (ask mpi >>> step (PathFragmentStep i)) x
@@ -447,12 +461,26 @@ instance Issuable 'PathLevel where
     = OperationMissing OperationMethod
     deriving stock (Eq, Ord, Show)
   issueIsUnsupported _ = False
+  describeIssue (OperationMissing op) = para $ "Method " <> strong (showMethod op) <> " is not defined."
 
 instance Behavable 'PathLevel 'OperationLevel where
   data Behave 'PathLevel 'OperationLevel
     = InOperation OperationMethod
     deriving (Eq, Ord, Show)
 
+  describeBehaviour (InOperation method) = showMethod method
+
+showMethod :: IsString s => OperationMethod -> s
+showMethod = \case
+  GetMethod -> "GET"
+  PutMethod -> "PUT"
+  PostMethod -> "POST"
+  DeleteMethod -> "DELETE"
+  OptionsMethod -> "OPTIONS"
+  HeadMethod -> "HEAD"
+  PatchMethod -> "PATCH"
+  TraceMethod -> "TRACE"
+
 instance Subtree MatchedPathItem where
   type SubtreeLevel MatchedPathItem = 'PathLevel
   type
@@ -550,6 +578,7 @@ instance Issuable 'CallbackLevel where
     deriving (Eq, Ord, Show)
   issueIsUnsupported = \case
     CallbacksUnsupported -> True
+  describeIssue CallbacksUnsupported = para "OpenApi Diff does not currently support callbacks."
 
 tracedCallbackPathItems :: Traced Callback -> Traced ProcessedPathItems
 tracedCallbackPathItems (Traced t (Callback x)) =
@@ -562,3 +591,5 @@ instance Steppable Callback ProcessedPathItems where
 instance Behavable 'OperationLevel 'CallbackLevel where
   data Behave 'OperationLevel 'CallbackLevel = OperationCallback Text
     deriving stock (Eq, Ord, Show)
+
+  describeBehaviour (OperationCallback key) = "Operation " <> code key
diff --git a/src/OpenAPI/Checker/Validate/Param.hs b/src/OpenAPI/Checker/Validate/Param.hs
index af7e339..8bd05be 100644
--- a/src/OpenAPI/Checker/Validate/Param.hs
+++ b/src/OpenAPI/Checker/Validate/Param.hs
@@ -6,7 +6,7 @@ module OpenAPI.Checker.Validate.Param
   , Issue (..)
   ) where
 
-import Control.Lens
+import Control.Lens hiding (para)
 import Control.Monad
 import Data.Maybe
 import Data.OpenApi
@@ -15,6 +15,7 @@ import OpenAPI.Checker.Behavior
 import OpenAPI.Checker.Orphans ()
 import OpenAPI.Checker.Subtree
 import OpenAPI.Checker.Validate.Schema ()
+import Text.Pandoc.Builder
 
 -- | The type is normalized encoding style of the parameter. If two encoding
 -- styles are equal then parameters are compatible with their encoding style
@@ -62,11 +63,20 @@ instance Issuable 'PathFragmentLevel where
     | PathFragmentsDontMatch Text Text
     deriving (Eq, Ord, Show)
   issueIsUnsupported _ = False
+  describeIssue ParamNameMismatch = para "The path fragments don't match."
+  describeIssue ParamEmptinessIncompatible = para "Expected that an empty parameter is allowed, but it isn't."
+  describeIssue ParamRequired = para "Expected the parameter to be optional, but it is required."
+  describeIssue ParamPlaceIncompatible = para "Parameters in incompatible locations."
+  describeIssue ParamStyleMismatch = para "Different parameter styles (encodings)."
+  describeIssue ParamSchemaMismatch = para "Expected a schema, but didn't find one."
+  describeIssue (PathFragmentsDontMatch e a) = para $ "Expected " <> code e <> " but got " <> code a <> "."
 
 instance Behavable 'PathFragmentLevel 'SchemaLevel where
   data Behave 'PathFragmentLevel 'SchemaLevel
     = InParamSchema
     deriving (Eq, Ord, Show)
+  
+  describeBehaviour InParamSchema = "JSON Schema"
 
 instance Subtree Param where
   type SubtreeLevel Param = 'PathFragmentLevel
diff --git a/src/OpenAPI/Checker/Validate/PathFragment.hs b/src/OpenAPI/Checker/Validate/PathFragment.hs
index 6d59b75..d0d7c53 100644
--- a/src/OpenAPI/Checker/Validate/PathFragment.hs
+++ b/src/OpenAPI/Checker/Validate/PathFragment.hs
@@ -32,7 +32,7 @@ parsePath = fmap partition . T.splitOn "/" . T.pack
 data PathFragment param
   = StaticPath Text
   | DynamicPath param
-  deriving stock (Eq, Ord)
+  deriving stock (Eq, Ord, Show, Functor)
 
 type PathFragmentParam = PathFragment (Traced Param)
 
diff --git a/src/OpenAPI/Checker/Validate/RequestBody.hs b/src/OpenAPI/Checker/Validate/RequestBody.hs
index 973419b..17020f4 100644
--- a/src/OpenAPI/Checker/Validate/RequestBody.hs
+++ b/src/OpenAPI/Checker/Validate/RequestBody.hs
@@ -2,6 +2,7 @@
 
 module OpenAPI.Checker.Validate.RequestBody
   ( Issue (..)
+  , Behave (..)
   )
 where
 
@@ -10,11 +11,13 @@ import Data.HashMap.Strict.InsOrd as IOHM
 import Data.Map.Strict as M
 import Data.Maybe
 import Data.OpenApi
+import qualified Data.Text as T
 import Network.HTTP.Media (MediaType)
 import OpenAPI.Checker.Behavior
 import OpenAPI.Checker.Subtree
 import OpenAPI.Checker.Validate.MediaTypeObject
 import OpenAPI.Checker.Validate.Sums
+import Text.Pandoc.Builder
 
 -- TODO: Use RequestMediaTypeObjectMapping
 tracedContent :: Traced RequestBody -> IOHM.InsOrdHashMap MediaType (Traced MediaTypeObject)
@@ -28,11 +31,16 @@ instance Issuable 'RequestLevel where
     | RequestMediaTypeNotFound MediaType
     deriving stock (Eq, Ord, Show)
   issueIsUnsupported _ = False
+  describeIssue RequestBodyRequired =
+    para "Expected the request body to be optional, but found it to be required."
+  describeIssue (RequestMediaTypeNotFound t) =
+    para $ "Couldn't find a request body for media type " <> (code . T.pack . show $ t) <> "."
 
 instance Behavable 'RequestLevel 'PayloadLevel where
   data Behave 'RequestLevel 'PayloadLevel
     = InPayload
     deriving stock (Eq, Ord, Show)
+  describeBehaviour InPayload = "Payload"
 
 instance Subtree RequestBody where
   type SubtreeLevel RequestBody = 'RequestLevel
diff --git a/src/OpenAPI/Checker/Validate/Responses.hs b/src/OpenAPI/Checker/Validate/Responses.hs
index 9242009..6d67e2a 100644
--- a/src/OpenAPI/Checker/Validate/Responses.hs
+++ b/src/OpenAPI/Checker/Validate/Responses.hs
@@ -2,7 +2,7 @@
 {-# OPTIONS_GHC -fno-warn-name-shadowing #-}
 
 module OpenAPI.Checker.Validate.Responses
-  (
+  ( Behave (..)
   )
 where
 
@@ -11,6 +11,7 @@ import Data.HashMap.Strict.InsOrd as IOHM
 import Data.Map.Strict as M
 import Data.Maybe
 import Data.OpenApi
+import qualified Data.Text as T
 import Network.HTTP.Media (MediaType)
 import OpenAPI.Checker.Behavior
 import OpenAPI.Checker.References
@@ -21,6 +22,7 @@ import OpenAPI.Checker.Validate.MediaTypeObject
 import OpenAPI.Checker.Validate.Products
 import OpenAPI.Checker.Validate.Schema ()
 import OpenAPI.Checker.Validate.Sums
+import Text.Pandoc.Builder
 
 tracedResponses :: Traced Responses -> IOHM.InsOrdHashMap HttpStatusCode (Traced (Referenced Response))
 tracedResponses resp =
@@ -70,17 +72,25 @@ instance Issuable 'ResponseLevel where
     | ResponseHeaderMissing HeaderName
     deriving stock (Eq, Ord, Show)
   issueIsUnsupported _ = False
+  describeIssue (ResponseMediaTypeMissing t) =
+    para $ "Couldn't find reponse for media type " <> (code . T.pack . show $ t) <> "."
+  describeIssue (ResponseHeaderMissing h) =
+    para $ "Couldn't find header " <> code h <> "."
 
 instance Behavable 'ResponseLevel 'PayloadLevel where
   data Behave 'ResponseLevel 'PayloadLevel
     = ResponsePayload
     deriving stock (Eq, Ord, Show)
 
+  describeBehaviour ResponsePayload = "Payload"
+
 instance Behavable 'ResponseLevel 'HeaderLevel where
   data Behave 'ResponseLevel 'HeaderLevel
     = InHeader HeaderName
     deriving stock (Eq, Ord, Show)
 
+  describeBehaviour (InHeader name) = "Header " <> code name
+
 instance Subtree Response where
   type SubtreeLevel Response = 'ResponseLevel
   type
diff --git a/src/OpenAPI/Checker/Validate/Schema.hs b/src/OpenAPI/Checker/Validate/Schema.hs
index f540b21..62f81ef 100644
--- a/src/OpenAPI/Checker/Validate/Schema.hs
+++ b/src/OpenAPI/Checker/Validate/Schema.hs
@@ -17,12 +17,13 @@ import Algebra.Lattice
 import Control.Applicative
 import Control.Arrow
 import Control.Comonad.Env hiding (env)
-import Control.Lens hiding (cons)
+import Control.Lens hiding (cons, para)
 import Control.Monad.Reader hiding (ask)
 import qualified Control.Monad.Reader as R
 import Control.Monad.State
 import Control.Monad.Writer
 import qualified Data.Aeson as A
+import qualified Data.ByteString.Lazy as BSL
 import Data.Coerce
 import qualified Data.Foldable as F
 import Data.HList
@@ -40,8 +41,8 @@ import Data.Scientific
 import qualified Data.Set as S
 import Data.Text (Text)
 import qualified Data.Text as T hiding (singleton)
+import qualified Data.Text.Encoding as T
 import Data.Typeable
-import Text.Regex.Pcre2
 import OpenAPI.Checker.Behavior
 import OpenAPI.Checker.Memo
 import OpenAPI.Checker.Orphans ()
@@ -49,6 +50,8 @@ import OpenAPI.Checker.Paths
 import qualified OpenAPI.Checker.PathsPrefixTree as P
 import OpenAPI.Checker.References
 import OpenAPI.Checker.Subtree
+import Text.Pandoc.Builder hiding (Format, Null)
+import Text.Regex.Pcre2
 
 -- | Type of a JSON value
 data JsonType
@@ -84,7 +87,7 @@ untypeValue (TArray a) = A.Array a
 untypeValue (TObject o) = A.Object o
 
 data Bound a = Exclusive !a | Inclusive !a
-  deriving (Eq, Show)
+  deriving (Eq, Show, Functor)
 
 -- | The order is lexicographical on @a * Bool@.
 instance Ord a => Ord (Bound a) where
@@ -128,6 +131,45 @@ data Condition :: JsonType -> Type where
   MaxProperties :: !Integer -> Condition 'Object
   MinProperties :: !Integer -> Condition 'Object
 
+showCondition :: Condition a -> Blocks
+showCondition = \case
+  (Exactly v) -> para "The value should be:" <> showJSONValue (untypeValue v)
+  (Maximum b) -> para $ "The value should be less than " <> showBound b <> "."
+  (Minimum (Down b)) -> para $ "The value should be more than " <> showBound (getDown <$> b) <> "."
+  (MultipleOf n) -> para $ "The value should be a multiple of " <> show' n <> "."
+  (NumberFormat p) -> para $ "The number should have the following format:" <> code p <> "."
+  (Pattern p) -> para "The value should satisfy the following pattern (regular expression):" <> codeBlock p
+  (StringFormat p) -> para $ "The string should have the following format:" <> code p <> "."
+  (MaxLength p) -> para $ "The length of the string should be less than or equal to " <> show' p <> "."
+  (MinLength p) -> para $ "The length of the string should be more than or equal to " <> show' p <> "."
+  (Items i _) -> para "The items of the array should satisfy:" <> showForEachJsonFormula i
+  (MaxItems n) -> para $ "The length of the array should be less than or equal to " <> show' n <> "."
+  (MinItems n) -> para $ "The length of the array should be more than or equal to " <> show' n <> "."
+  UniqueItems -> para "The elements in the array should be unique."
+  (Properties props additional _) ->
+    bulletList $
+      (M.toList props
+         <&> (\(k, p) ->
+                para (code k)
+                  <> para (strong $ if propRequired p then "Required" else "Optional")
+                  <> showForEachJsonFormula (propFormula p)))
+        <> [ para (emph "Additional properties")
+               <> showForEachJsonFormula additional
+           ]
+  (MaxProperties n) -> para $ "The maximum number of fields should be " <> show' n <> "."
+  (MinProperties n) -> para $ "The minimum number of fields should be " <> show' n <> "."
+  where
+    showForEachJsonFormula :: ForeachType JsonFormula -> Blocks
+    showForEachJsonFormula i =
+      bulletList $
+        foldType
+          (\t f ->
+             let (DNF conds') = f i
+                 conds = S.toList <$> S.toList conds'
+              in [ para (describeJSONType t)
+                     <> bulletList (conds <&> \cond -> bulletList (showCondition <$> cond))
+                 ])
+
 satisfiesTyped :: TypedValue t -> Condition t -> Bool
 satisfiesTyped e (Exactly e') = e == e'
 satisfiesTyped (TNumber n) (Maximum (Exclusive m)) = n < m
@@ -363,10 +405,6 @@ instance
       , forObject = top
       }
 
-instance Behavable 'SchemaLevel 'SchemaLevel where
-  data Behave 'SchemaLevel 'SchemaLevel
-    deriving (Eq, Ord, Show)
-
 instance Steppable Schema (Referenced Schema) where
   data Step Schema (Referenced Schema)
     = AllOfStep Int
@@ -396,7 +434,7 @@ parseDiscriminatorValue v = case A.fromJSON @(Referenced Schema) $ A.object ["$r
   A.Error _ -> Ref $ Reference v
 
 -- | A fake writer monad that doesn't actually record anything and allows lazy recursion.
-newtype Silent q f r a = Silent { runSilent :: a }
+newtype Silent q f r a = Silent {runSilent :: a}
   deriving stock (Functor)
   deriving (Applicative, Monad) via Identity
 
@@ -427,11 +465,12 @@ silently m = do
   pure . runSilent $ runReaderT m defs
 
 warnKnot :: MonadProcess m => KnotTier (ForeachType JsonFormula) () m
-warnKnot = KnotTier
-  { onKnotFound = warn UnguardedRecursion
-  , onKnotUsed = \_ -> pure bottom
-  , tieKnot = \_ -> pure
-  }
+warnKnot =
+  KnotTier
+    { onKnotFound = warn UnguardedRecursion
+    , onKnotUsed = \_ -> pure bottom
+    , tieKnot = \_ -> pure
+    }
 
 processRefSchema
   :: MonadProcess m
@@ -835,19 +874,19 @@ checkImplication env beh prods cons = case findExactly prods of
       Just m' ->
         if m' <= m
           then pure ()
-          else issueAt beh (MatchingMaximumWeak m m')
+          else issueAt beh (MatchingMaximumWeak $ ProdCons {producer = m', consumer = m})
       Nothing -> issueAt beh (NoMatchingMaximum m)
     Minimum m -> case findRelevant max (\case Minimum m' -> Just m'; _ -> Nothing) prods of
       Just m' ->
         if m' >= m
           then pure ()
-          else issueAt beh (MatchingMinimumWeak (coerce m) (coerce m'))
+          else issueAt beh (MatchingMinimumWeak ProdCons {producer = coerce m', consumer = coerce m})
       Nothing -> issueAt beh (NoMatchingMinimum (coerce m))
     MultipleOf m -> case findRelevant lcmScientific (\case MultipleOf m' -> Just m'; _ -> Nothing) prods of
       Just m' ->
         if lcmScientific m m' == m'
           then pure ()
-          else issueAt beh (MatchingMultipleOfWeak m m')
+          else issueAt beh (MatchingMultipleOfWeak $ ProdCons {producer = m', consumer = m})
       Nothing -> issueAt beh (NoMatchingMultipleOf m)
     NumberFormat f ->
       if any (\case NumberFormat f' -> f == f'; _ -> False) prods
@@ -857,13 +896,13 @@ checkImplication env beh prods cons = case findExactly prods of
       Just m' ->
         if m' <= m
           then pure ()
-          else issueAt beh (MatchingMaxLengthWeak m m')
+          else issueAt beh (MatchingMaxLengthWeak $ ProdCons {producer = m', consumer = m})
       Nothing -> issueAt beh (NoMatchingMaxLength m)
     MinLength m -> case findRelevant max (\case MinLength m' -> Just m'; _ -> Nothing) prods of
       Just m' ->
         if m' >= m
           then pure ()
-          else issueAt beh (MatchingMinLengthWeak m m')
+          else issueAt beh (MatchingMinLengthWeak $ ProdCons {producer = m', consumer = m})
       Nothing -> issueAt beh (NoMatchingMinLength m)
     Pattern p ->
       if any (\case Pattern p' -> p == p'; _ -> False) prods
@@ -883,50 +922,52 @@ checkImplication env beh prods cons = case findExactly prods of
       Just m' ->
         if m' <= m
           then pure ()
-          else issueAt beh (MatchingMaxItemsWeak m m')
+          else issueAt beh (MatchingMaxItemsWeak ProdCons {producer = m', consumer = m})
       Nothing -> issueAt beh (NoMatchingMaxItems m)
     MinItems m -> case findRelevant max (\case MinItems m' -> Just m'; _ -> Nothing) prods of
       Just m' ->
         if m' >= m
           then pure ()
-          else issueAt beh (MatchingMinItemsWeak m m')
+          else issueAt beh (MatchingMinItemsWeak ProdCons {producer = m', consumer = m})
       Nothing -> issueAt beh (NoMatchingMinItems m)
     UniqueItems ->
       if any (== UniqueItems) $ prods
         then pure ()
         else issueAt beh NoMatchingUniqueItems
     Properties props _ madd -> case findRelevant (<>) (\case Properties props' _ madd' -> Just $ (props', madd') NE.:| []; _ -> Nothing) prods of
-      Just pm -> anyOfAt beh NoMatchingProperties $ NE.toList pm <&> \(props', madd') -> do
-        F.for_ (S.fromList $ M.keys props <> M.keys props') $ \k -> do
-          let go sch sch' = checkCompatibility env (beh >>> step (InProperty k)) (ProdCons sch sch')
-          case (M.lookup k props', madd', M.lookup k props, madd) of
-            (Nothing, Nothing, _, _) -> pure () -- vacuously
-            (_, _, Nothing, Nothing) -> issueAt beh (UnexpectedProperty k)
-            (Just p', _, Just p, _) -> go (propRefSchema p') (propRefSchema p)
-            (Nothing, Just add', Just p, _) -> go add' (propRefSchema p)
-            (Just p', _, Nothing, Just add) -> go (propRefSchema p') add
-            (Nothing, Just _, Nothing, Just _) -> pure ()
-          case (maybe False propRequired $ M.lookup k props', maybe False propRequired $ M.lookup k props) of
-            (False, True) -> issueAt beh (PropertyNowRequired k)
-            _ -> pure ()
-          pure ()
-        case (madd', madd) of
-          (Nothing, _) -> pure () -- vacuously
-          (_, Nothing) -> issueAt beh NoAdditionalProperties
-          (Just add', Just add) -> checkCompatibility env (beh >>> step InAdditionalProperty) (ProdCons add' add)
-        pure ()
+      Just pm ->
+        anyOfAt beh NoMatchingProperties $
+          NE.toList pm <&> \(props', madd') -> do
+            F.for_ (S.fromList $ M.keys props <> M.keys props') $ \k -> do
+              let go sch sch' = checkCompatibility env (beh >>> step (InProperty k)) (ProdCons sch sch')
+              case (M.lookup k props', madd', M.lookup k props, madd) of
+                (Nothing, Nothing, _, _) -> pure () -- vacuously
+                (_, _, Nothing, Nothing) -> issueAt beh (UnexpectedProperty k)
+                (Just p', _, Just p, _) -> go (propRefSchema p') (propRefSchema p)
+                (Nothing, Just add', Just p, _) -> go add' (propRefSchema p)
+                (Just p', _, Nothing, Just add) -> go (propRefSchema p') add
+                (Nothing, Just _, Nothing, Just _) -> pure ()
+              case (maybe False propRequired $ M.lookup k props', maybe False propRequired $ M.lookup k props) of
+                (False, True) -> issueAt beh (PropertyNowRequired k)
+                _ -> pure ()
+              pure ()
+            case (madd', madd) of
+              (Nothing, _) -> pure () -- vacuously
+              (_, Nothing) -> issueAt beh NoAdditionalProperties
+              (Just add', Just add) -> checkCompatibility env (beh >>> step InAdditionalProperty) (ProdCons add' add)
+            pure ()
       Nothing -> issueAt beh NoMatchingProperties
     MaxProperties m -> case findRelevant min (\case MaxProperties m' -> Just m'; _ -> Nothing) prods of
       Just m' ->
         if m' <= m
           then pure ()
-          else issueAt beh (MatchingMaxPropertiesWeak m m')
+          else issueAt beh (MatchingMaxPropertiesWeak ProdCons {producer = m', consumer = m})
       Nothing -> issueAt beh (NoMatchingMaxProperties m)
     MinProperties m -> case findRelevant max (\case MinProperties m' -> Just m'; _ -> Nothing) prods of
       Just m' ->
         if m' >= m
           then pure ()
-          else issueAt beh (MatchingMinPropertiesWeak m m')
+          else issueAt beh (MatchingMinPropertiesWeak ProdCons {producer = m', consumer = m})
       Nothing -> issueAt beh (NoMatchingMinProperties m)
   where
     findExactly (Exactly x : _) = Just x
@@ -939,85 +980,145 @@ checkImplication env beh prods cons = case findExactly prods of
 
 instance Issuable 'TypedSchemaLevel where
   data Issue 'TypedSchemaLevel
-    = EnumDoesntSatisfy A.Value
-    -- ^ producer produces a specific value ($1), consumer has a condition that is not satisfied by said value
-    | NoMatchingEnum A.Value
-    -- ^ producer produces a specific value ($1) which is not listed in the consumer's list of specific values
-    | NoMatchingMaximum (Bound Scientific)
-    -- ^ producer declares a maximum numeric value ($1), consumer doesnt
-    | MatchingMaximumWeak (Bound Scientific) (Bound Scientific)
-    -- ^ producer declares a maximum numeric value ($1), consumer declares a weaker (higher) limit ($2)
-    | NoMatchingMinimum (Bound Scientific)
-    -- ^ producer declares a minimum numeric value, consumer doesnt
-    | MatchingMinimumWeak (Bound Scientific) (Bound Scientific)
-    -- ^ producer declares a minimum numeric value ($1), consumer declares a weaker (lower) limit ($2)
-    | NoMatchingMultipleOf Scientific
-    -- ^ producer declares that the numeric value must be a multiple of $1, consumer doesn't
-    | MatchingMultipleOfWeak Scientific Scientific
-    -- ^ producer declares that the numeric value must be a multiple of $1, consumer declares a weaker condition (multiple of $2)
-    | NoMatchingFormat Format
-    -- ^ producer declares a string/number format, consumer declares none or a different format (TODO: improve via regex #32)
-    | NoMatchingMaxLength Integer
-    -- ^ producer declares a maximum length of the string ($1), consumer doesn't.
-    | MatchingMaxLengthWeak Integer Integer
-    -- ^ producer declares a maximum length of the string ($1), consumer declares a weaker (higher) limit ($2)
-    | NoMatchingMinLength Integer
-    -- ^ producer declares a minimum length of the string ($1), consumer doesn't.
-    | MatchingMinLengthWeak Integer Integer
-    -- ^ producer declares a minimum length of the string ($1), consumer declares a weaker (lower) limit ($2)
-    | NoMatchingPattern Pattern
-    -- ^ producer declares the string value must matrix a regex ($1), consumer doesn't declare or declares different regex (TODO: #32)
-    | NoMatchingItems
-    -- ^ producer declares the items of an array must satisfy some condition, consumer doesn't
-    | NoMatchingMaxItems Integer
-    -- ^ producer declares a maximum length of the array ($1), consumer doesn't.
-    | MatchingMaxItemsWeak Integer Integer
-    -- ^ producer declares a maximum length of the array ($1), consumer declares a weaker (higher) limit ($2)
-    | NoMatchingMinItems Integer
-    -- ^ producer declares a minimum length of the array ($1), consumer doesn't.
-    | MatchingMinItemsWeak Integer Integer
-    -- ^ producer declares a minimum length of the array ($1), consumer declares a weaker (lower) limit ($2)
-    | NoMatchingUniqueItems
-    -- ^ producer declares that items must be unique, consumer doesn't
-    | NoMatchingProperties
-    -- ^ producer declares the properties of an object must satisfy some condition, consumer doesn't
-    | UnexpectedProperty Text
-    -- ^ producer allows a property that is not allowed in the consumer
-    | PropertyNowRequired Text
-    -- ^ consumer requires a property that is not required/allowed in the consumer
-    | NoAdditionalProperties
-    -- ^ producer allows additional properties, consumer doesn't
-    | NoMatchingMaxProperties Integer
-    -- ^ producer declares a maximum number of properties in the object ($1), consumer doesn't.
-    | MatchingMaxPropertiesWeak Integer Integer
-    -- ^ producer declares a maximum number of properties in the object ($1), consumer declares a weaker (higher) limit ($2)
-    | NoMatchingMinProperties Integer
-    -- ^ producer declares a minimum number of properties in the object ($1), consumer doesn't.
-    | MatchingMinPropertiesWeak Integer Integer
-    -- ^ producer declares a minimum number of properties in the object ($1), consumer declares a weaker (lower) limit ($2)
-    | NoMatchingCondition [SomeCondition]
-    -- ^ consumer declares that the value must satisfy a disjunction of some conditions, but producer's requirements couldn't be matched against any single one of them (TODO: split heuristic #71)
-    | NoContradiction
-    -- ^ producer indicates that values of this type are now allowed, but the consumer does not do so (currently we only check immediate contradictions, c.f. #70)
+    = -- | producer produces a specific value ($1), consumer has a condition that is not satisfied by said value
+      EnumDoesntSatisfy A.Value
+    | -- | consumer only expects a specific value which the producer does not produce.
+      NoMatchingEnum A.Value
+    | -- | consumer declares a maximum numeric value ($1), producer doesn't
+      NoMatchingMaximum (Bound Scientific)
+    | -- | consumer declares a maximum numeric value ($1), producer declares a weaker (higher) limit ($2)
+      MatchingMaximumWeak (ProdCons (Bound Scientific))
+    | -- | consumer declares a minimum numeric value, producer doesn't
+      NoMatchingMinimum (Bound Scientific)
+    | -- | consumer declares a minimum numeric value ($1), producer declares a weaker (lower) limit ($2)
+      MatchingMinimumWeak (ProdCons (Bound Scientific))
+    | -- | consumer declares that the numeric value must be a multiple of $1, producer doesn't
+      NoMatchingMultipleOf Scientific
+    | -- | consumer declares that the numeric value must be a multiple of $1, producer declares a weaker condition (multiple of $2)
+      MatchingMultipleOfWeak (ProdCons Scientific)
+    | -- | consumer declares a string/number format, producer declares none or a different format (TODO: improve via regex #32)
+      NoMatchingFormat Format
+    | -- | consumer declares a maximum length of the string ($1), producer doesn't.
+      NoMatchingMaxLength Integer
+    | -- | consumer declares a maximum length of the string ($1), producer declares a weaker (higher) limit ($2)
+      MatchingMaxLengthWeak (ProdCons Integer)
+    | -- | consumer declares a minimum length of the string ($1), producer doesn't.
+      NoMatchingMinLength Integer
+    | -- | consumer declares a minimum length of the string ($1), producer declares a weaker (lower) limit ($2)
+      MatchingMinLengthWeak (ProdCons Integer)
+    | -- | consumer declares the string value must matrix a regex ($1), producer doesn't declare or declares different regex (TODO: #32)
+      NoMatchingPattern Pattern
+    | -- | consumer declares the items of an array must satisfy some condition, producer doesn't
+      NoMatchingItems
+    | -- | consumer declares a maximum length of the array ($1), producer doesn't.
+      NoMatchingMaxItems Integer
+    | -- | consumer declares a maximum length of the array ($1), producer declares a weaker (higher) limit ($2)
+      MatchingMaxItemsWeak (ProdCons Integer)
+    | -- | consumer declares a minimum length of the array ($1), producer doesn't.
+      NoMatchingMinItems Integer
+    | -- | consumer declares a minimum length of the array ($1), producer declares a weaker (lower) limit ($2)
+      MatchingMinItemsWeak (ProdCons Integer)
+    | -- | consumer declares that items must be unique, producer doesn't
+      NoMatchingUniqueItems
+    | -- | consumer declares the properties of an object must satisfy some condition, producer doesn't
+      NoMatchingProperties
+    | -- | producer allows a property that is not allowed in the consumer
+      UnexpectedProperty Text
+    | -- | consumer requires a property that is not required/allowed in the producer
+      PropertyNowRequired Text
+    | -- | producer allows additional properties, consumer doesn't
+      NoAdditionalProperties
+    | -- | consumer declares a maximum number of properties in the object ($1), producer doesn't.
+      NoMatchingMaxProperties Integer
+    | -- | consumer declares a maximum number of properties in the object ($1), producer declares a weaker (higher) limit ($2)
+      MatchingMaxPropertiesWeak (ProdCons Integer)
+    | -- | consumer declares a minimum number of properties in the object ($1), producer doesn't.
+      NoMatchingMinProperties Integer
+    | -- | consumer declares a minimum number of properties in the object ($1), producer declares a weaker (lower) limit ($2)
+      MatchingMinPropertiesWeak (ProdCons Integer)
+    | -- | consumer declares that the value must satisfy a disjunction of some conditions, but producer's requirements couldn't be matched against any single one of them (TODO: split heuristic #71)
+      NoMatchingCondition [SomeCondition]
+    | -- | consumer indicates that values of this type are now allowed, but the producer does not do so (currently we only check immediate contradictions, c.f. #70)
+      NoContradiction
     deriving stock (Eq, Ord, Show)
   issueIsUnsupported _ = False
+  describeIssue (EnumDoesntSatisfy v) = para "The following enum value will yield an error:" <> showJSONValue v
+  describeIssue (NoMatchingEnum v) = para "The following enum value is not supported:" <> showJSONValue v
+  describeIssue (NoMatchingMaximum b) = para $ "Unexpected upper bound " <> showBound b <> "."
+  describeIssue (MatchingMaximumWeak (ProdCons p c)) = para $ "Expected upper bound " <> showBound p <> " but but found " <> showBound c <> "."
+  describeIssue (NoMatchingMinimum b) = para $ "Unexpected lower bound " <> showBound b <> "."
+  describeIssue (MatchingMinimumWeak (ProdCons p c)) = para $ "Expected lower bound " <> showBound p <> " but but found " <> showBound c <> "."
+  describeIssue (NoMatchingMultipleOf n) = para $ "Didn't expect the value to be a multiple of " <> show' n <> " but it was."
+  describeIssue (MatchingMultipleOfWeak (ProdCons p c)) = para $ "Expected the value to be a multiple of " <> show' p <> " but found a multiple of " <> show' c <> "."
+  describeIssue (NoMatchingFormat f) = para $ "Unexpected format: " <> code f <> "."
+  describeIssue (NoMatchingMaxLength n) = para $ "Unexpected maximum length of the string " <> show' n <> "."
+  describeIssue (MatchingMaxLengthWeak (ProdCons p c)) = para $ "Expected the maximum length of the string to be " <> show' p <> "but it was " <> show' c <> "."
+  describeIssue (NoMatchingMinLength n) = para $ "Unexpected minimum length of the string " <> show' n <> "."
+  describeIssue (MatchingMinLengthWeak (ProdCons p c)) = para $ "Expected the minimum length of the string to be " <> show' p <> "but it was " <> show' c <> "."
+  describeIssue (NoMatchingPattern p) = para "Unexpected pattern (regular expression): " <> codeBlock p
+  describeIssue NoMatchingItems = para "Couldn't find any matching items."
+  describeIssue (NoMatchingMaxItems n) = para $ "Unexpected maximum length of the array " <> show' n <> "."
+  describeIssue (MatchingMaxItemsWeak (ProdCons p c)) = para $ "Expected the maximum length of the array to be " <> show' p <> "but it was " <> show' c <> "."
+  describeIssue (NoMatchingMinItems n) = para $ "Unexpected minimum length of the array " <> show' n <> "."
+  describeIssue (MatchingMinItemsWeak (ProdCons p c)) = para $ "Expected the minimum length of the array to be " <> show' p <> "but it was " <> show' c <> "."
+  describeIssue NoMatchingUniqueItems = para "Didn't expect the items to be unique, but they were."
+  describeIssue NoMatchingProperties = para "Couldn't find matching properties."
+  describeIssue (UnexpectedProperty p) = para $ "Expected the property " <> code p <> " to be allowed, but it wasn't."
+  describeIssue (PropertyNowRequired p) = para $ "Don't have a required property " <> code p <> "."
+  describeIssue NoAdditionalProperties = para "Expected additional properties to be allowed, but they weren't."
+  describeIssue (NoMatchingMaxProperties n) = para $ "Unexpected maximum number of properties " <> show' n <> "."
+  describeIssue (MatchingMaxPropertiesWeak (ProdCons p c)) = para $ "Expected the maximum  number of properties to be " <> show' p <> "but it was " <> show' c <> "."
+  describeIssue (NoMatchingMinProperties n) = para $ "Unexpected minimum number of properties " <> show' n <> "."
+  describeIssue (MatchingMinPropertiesWeak (ProdCons p c)) = para $ "Expected the minimum  number of properties to be " <> show' p <> "but it was " <> show' c <> "."
+  describeIssue (NoMatchingCondition conds) =
+    para "Expected the following conditions to hold, but they didn't:"
+      <> bulletList ((\(SomeCondition c) -> showCondition c) <$> conds)
+  describeIssue NoContradiction = para "Expected the type to be allowed, but it wasn't."
+
+showJSONValue :: A.Value -> Blocks
+showJSONValue v = codeBlockWith ("", ["json"], mempty) (T.decodeUtf8 . BSL.toStrict . A.encode $ v)
+
+showBound :: Show a => Bound a -> Inlines
+showBound (Inclusive x) = show' x <> " inclusive"
+showBound (Exclusive x) = show' x <> " exclusive"
+
+show' :: Show x => x -> Inlines
+show' = str . T.pack . show
 
 instance Issuable 'SchemaLevel where
   data Issue 'SchemaLevel
-    = NotSupported Text
-    -- ^ Some (openapi-supported) feature that we do not support was encountered in the schema
-    | InvalidSchema Text
-    -- ^ The schema is actually invalid
-    | UnguardedRecursion
-    -- ^ The schema contains a reference loop along "anyOf"/"allOf"/"oneOf".
+    = -- | Some (openapi-supported) feature that we do not support was encountered in the schema
+      NotSupported Text
+    | -- | The schema is actually invalid
+      InvalidSchema Text
+    | -- | The schema contains a reference loop along "anyOf"/"allOf"/"oneOf".
+      UnguardedRecursion
     deriving stock (Eq, Ord, Show)
   issueIsUnsupported _ = True
 
+  describeIssue (NotSupported i) =
+    para (emph "Encountered a feature that OpenApi Diff does not support: " <> text i <> ".")
+  describeIssue (InvalidSchema i) =
+    para (emph "The schema is invalid: " <> text i <> ".")
+  describeIssue UnguardedRecursion =
+    para "Encountered recursion that is too complex for OpenApi Diff to untangle."
+
 instance Behavable 'SchemaLevel 'TypedSchemaLevel where
   data Behave 'SchemaLevel 'TypedSchemaLevel
     = OfType JsonType
     deriving stock (Eq, Ord, Show)
 
+  describeBehaviour (OfType t) = describeJSONType t
+
+describeJSONType :: JsonType -> Inlines
+describeJSONType = \case
+  Null -> "Null"
+  Boolean -> "Boolean"
+  Number -> "Number"
+  String -> "String"
+  Array -> "Array"
+  Object -> "Object"
+
 instance Behavable 'TypedSchemaLevel 'SchemaLevel where
   data Behave 'TypedSchemaLevel 'SchemaLevel
     = InItems
@@ -1025,6 +1126,10 @@ instance Behavable 'TypedSchemaLevel 'SchemaLevel where
     | InAdditionalProperty
     deriving stock (Eq, Ord, Show)
 
+  describeBehaviour InItems = "Items"
+  describeBehaviour (InProperty p) = "Property " <> code p
+  describeBehaviour InAdditionalProperty = "Additional properties"
+
 instance Subtree Schema where
   type SubtreeLevel Schema = 'SchemaLevel
   type CheckEnv Schema = '[ProdCons (Traced (Definitions Schema))]
diff --git a/src/OpenAPI/Checker/Validate/Server.hs b/src/OpenAPI/Checker/Validate/Server.hs
index 7192657..ed15e78 100644
--- a/src/OpenAPI/Checker/Validate/Server.hs
+++ b/src/OpenAPI/Checker/Validate/Server.hs
@@ -28,6 +28,7 @@ import OpenAPI.Checker.Common
 import OpenAPI.Checker.Paths
 import OpenAPI.Checker.Subtree
 import OpenAPI.Checker.Validate.MediaTypeObject
+import Text.Pandoc.Builder
 import Prelude as P
 
 tracedParsedServerUrlParts
@@ -45,6 +46,8 @@ instance Behavable 'OperationLevel 'ServerLevel where
     = InServer Text
     deriving stock (Eq, Ord, Show)
 
+  describeBehaviour (InServer n) = "Server " <> code n
+
 instance Subtree [Server] where
   type SubtreeLevel [Server] = 'OperationLevel
   type CheckEnv [Server] = '[]
@@ -131,6 +134,13 @@ instance Issuable 'ServerLevel where
     | ServerNotMatched
     deriving stock (Eq, Ord, Show)
   issueIsUnsupported _ = False
+  describeIssue (EnumValueNotConsumed _ v) =
+    para $ "Enum value " <> code v <> " is not supported."
+  describeIssue (ConsumerNotOpen _) =
+    para $ "Expected a variable to be open (any value), but it wasn't."
+  describeIssue (ServerVariableNotDefined k) =
+    para $ "Variable " <> code k <> " is not defined."
+  describeIssue ServerNotMatched = para $ "Couldn't find a matching server."
 
 instance Subtree ProcessedServer where
   type SubtreeLevel ProcessedServer = 'ServerLevel
diff --git a/stack.yaml b/stack.yaml
index b17acde..034398f 100644
--- a/stack.yaml
+++ b/stack.yaml
@@ -1 +1 @@
-resolver: lts-17.12
+resolver: nightly-2021-06-01
diff --git a/stack.yaml.lock b/stack.yaml.lock
index 9439c56..360dd4a 100644
--- a/stack.yaml.lock
+++ b/stack.yaml.lock
@@ -6,7 +6,7 @@
 packages: []
 snapshots:
 - completed:
-    size: 567669
-    url: https://raw.githubusercontent.com/commercialhaskell/stackage-snapshots/master/lts/17/12.yaml
-    sha256: facf6cac73b22a83ca955b580a98a7a09ed71f8f974c7a55d28e608c23e689a9
-  original: lts-17.12
+    size: 587963
+    url: https://raw.githubusercontent.com/commercialhaskell/stackage-snapshots/master/nightly/2021/6/1.yaml
+    sha256: 6f13285c82266d1d06f7f68366a5190dcbc6758ae8806813005cf56daa6bb9be
+  original: nightly-2021-06-01
diff --git a/test/Spec.hs b/test/Spec.hs
index 4001530..128e8bf 100644
--- a/test/Spec.hs
+++ b/test/Spec.hs
@@ -9,8 +9,4 @@ main = defaultMain =<< tests
 tests :: IO TestTree
 tests = do
   goldenReportTree <- Spec.Golden.TraceTree.tests
-  return . localOption (mkTimeout 1000000) $
-    testGroup
-      "Golden tests"
-      [ goldenReportTree
-      ]
+  return . localOption (mkTimeout 1000000) $ goldenReportTree
diff --git a/test/Spec/Golden/Extra.hs b/test/Spec/Golden/Extra.hs
index aa8c8c2..7f29b50 100644
--- a/test/Spec/Golden/Extra.hs
+++ b/test/Spec/Golden/Extra.hs
@@ -8,15 +8,11 @@ where
 
 import Control.Lens
 import Control.Monad
-import Data.Aeson hiding (Result)
 import qualified Data.ByteString.Lazy as BSL
-import qualified Data.Yaml as Yaml
-import OpenAPI.Checker.Subtree
 import System.Directory
 import System.FilePath
 import Test.Tasty
 import Test.Tasty.Golden
-import Test.Tasty.Providers
 
 data TestInput t
   = TestInputNode TestName [TestInput t]
@@ -54,62 +50,40 @@ getGoldenInputsUniform
 getGoldenInputsUniform name f filepath inp = getGoldenInputs name filepath $ inp & each %~ (,f)
 
 goldenInputsTree
-  :: (Each s t (FilePath, FilePath -> IO a) a, ToJSON x, HasUnsupportedFeature x)
+  :: (Each s t (FilePath, FilePath -> IO a) a)
   => TestName
   -> FilePath -- ^ Root path
   -> FilePath -- ^ Name of golden file
   -> s
-  -> (t -> x)
+  -> (t -> IO BSL.ByteString)
   -> IO TestTree
 goldenInputsTree name filepath golden inp f = do
   runTestInputTree golden f <$> getGoldenInputs name filepath inp
 
 runTestInputTree
-  :: (ToJSON x, HasUnsupportedFeature x)
-  => FilePath
-  -> (t -> x)
+  :: FilePath
+  -> (t -> IO BSL.ByteString)
   -> TestInput t
   -> TestTree
 runTestInputTree golden f (TestInputNode name rest) =
   testGroup name (runTestInputTree golden f <$> rest)
-runTestInputTree golden f (TestInputLeaf name t path)
-  | testSupported name =
-    goldenVsStringDiff
-      name
-      (\ref new -> ["diff", "-u", ref, new])
-      (path </> golden)
-      (pure . BSL.fromStrict . Yaml.encode . f $ t)
-runTestInputTree _ f (TestInputLeaf name t _) =
-  reportResult name $
-    if hasUnsupportedFeature (f t)
-      then testPassed "Feature unsupported"
-      else testFailed "Unexpected feature support"
-
-reportResult :: TestName -> Result -> TestTree
-reportResult name result = singleTest name $ SimpleTestReporter result
-
-newtype SimpleTestReporter = SimpleTestReporter Result
-
-instance IsTest SimpleTestReporter where
-  run _ (SimpleTestReporter result) _ = return result
-  testOptions = mempty
-
-testSupported :: TestName -> Bool
-testSupported ('x' : ' ' : _) = False
-testSupported _ = True
+runTestInputTree golden f (TestInputLeaf name t path) =
+  goldenVsStringDiff
+    name
+    (\ref new -> ["diff", "-u", ref, new])
+    (path </> golden)
+    (f t)
 
 goldenInputsTreeUniform
   :: ( Each t h (FilePath, FilePath -> IO a) a
-     , ToJSON x
      , Each s t FilePath (FilePath, FilePath -> IO a)
-     , HasUnsupportedFeature x
      )
   => String
   -> FilePath -- ^ Root path
   -> FilePath -- ^ Name of golden file
   -> s
   -> (FilePath -> IO a)
-  -> (h -> x)
+  -> (h -> IO BSL.ByteString)
   -> IO TestTree
 goldenInputsTreeUniform name filepath golden inp h =
   goldenInputsTree name filepath golden (inp & each %~ (,h))
diff --git a/test/Spec/Golden/TraceTree.hs b/test/Spec/Golden/TraceTree.hs
index 6138aa5..2bc0815 100644
--- a/test/Spec/Golden/TraceTree.hs
+++ b/test/Spec/Golden/TraceTree.hs
@@ -4,26 +4,56 @@ module Spec.Golden.TraceTree
 where
 
 import Control.Category
+import Control.Exception
+import qualified Data.ByteString.Lazy as BSL
+import Data.Default
 import Data.HList
+import Data.OpenApi
+import Data.Text (Text)
+import qualified Data.Text.Encoding as T
 import qualified Data.Yaml as Yaml
-import OpenAPI.Checker.Subtree
+import OpenAPI.Checker.Behavior
 import OpenAPI.Checker.Paths
+import OpenAPI.Checker.PathsPrefixTree
+import OpenAPI.Checker.Report
+import OpenAPI.Checker.Subtree
 import OpenAPI.Checker.Validate.OpenApi ()
 import Spec.Golden.Extra
-import Test.Tasty (TestTree)
+import Test.Tasty (TestTree, testGroup)
+import Text.Pandoc.Class
+import Text.Pandoc.Writers
 import Prelude hiding (id, (.))
 
 tests :: IO TestTree
-tests =
-  goldenInputsTreeUniform
-    "Golden TraceTree"
-    "test/golden/common"
-    "trace-tree.yaml"
-    ("a.yaml", "b.yaml")
-    Yaml.decodeFileThrow
-    (runCompatFormula . checkCompatibility HNil Root . toPC)
-    where
-      toPC (client, server) = ProdCons
-        { producer = traced (step ClientSchema) client
-        , consumer = traced (step ServerSchema) server
+tests = do
+  traceTreeTests <-
+    goldenInputsTreeUniform
+      "TraceTree"
+      "test/golden/common"
+      "trace-tree.yaml"
+      ("a.yaml", "b.yaml")
+      Yaml.decodeFileThrow
+      (pure . BSL.fromStrict . Yaml.encode . runChecker)
+
+  reportTests <-
+    goldenInputsTreeUniform
+      "Report"
+      "test/golden/common"
+      "report.md"
+      ("a.yaml", "b.yaml")
+      Yaml.decodeFileThrow
+      (runPandoc . writeMarkdown def . generateReport . runChecker)
+
+  return $ testGroup "Golden tests" [traceTreeTests, reportTests]
+
+runPandoc :: PandocPure Text -> IO BSL.ByteString
+runPandoc = either throwIO (pure . BSL.fromStrict . T.encodeUtf8) . runPure
+
+runChecker :: (OpenApi, OpenApi) -> Either (PathsPrefixTree Behave AnIssue 'APILevel) ()
+runChecker = runCompatFormula . checkCompatibility HNil Root . toPC
+  where
+    toPC (c, s) =
+      ProdCons
+        { producer = traced (step ClientSchema) c
+        , consumer = traced (step ServerSchema) s
         }
diff --git a/test/golden/common/enum-anyof/report.md b/test/golden/common/enum-anyof/report.md
new file mode 100644
index 0000000..4211f70
--- /dev/null
+++ b/test/golden/common/enum-anyof/report.md
@@ -0,0 +1 @@
+# No breaking changes found ✨
diff --git a/test/golden/common/id/report.md b/test/golden/common/id/report.md
new file mode 100644
index 0000000..4211f70
--- /dev/null
+++ b/test/golden/common/id/report.md
@@ -0,0 +1 @@
+# No breaking changes found ✨
diff --git a/test/golden/common/json/recursive/report.md b/test/golden/common/json/recursive/report.md
new file mode 100644
index 0000000..4211f70
--- /dev/null
+++ b/test/golden/common/json/recursive/report.md
@@ -0,0 +1 @@
+# No breaking changes found ✨
diff --git a/test/golden/common/maximum-lowered/report.md b/test/golden/common/maximum-lowered/report.md
new file mode 100644
index 0000000..4952135
--- /dev/null
+++ b/test/golden/common/maximum-lowered/report.md
@@ -0,0 +1,7 @@
+# **POST** /test
+
+## JSON Request
+
+### Number
+
+Expected upper bound 3.0 inclusive but but found 2.0 inclusive.
diff --git a/test/golden/common/maximum-lowered/trace-tree.yaml b/test/golden/common/maximum-lowered/trace-tree.yaml
index ff56896..bddbc8b 100644
--- a/test/golden/common/maximum-lowered/trace-tree.yaml
+++ b/test/golden/common/maximum-lowered/trace-tree.yaml
@@ -1,7 +1,8 @@
 Left:
-  AtPath (ProdCons {producer = "/test", consumer = "/test"}):
+  AtPath "/test":
     InOperation PostMethod:
       InRequest:
         InPayload:
           PayloadSchema:
-            OfType Number: MatchingMaximumWeak (Inclusive 2.0) (Inclusive 3.0)
+            OfType Number: MatchingMaximumWeak (ProdCons {producer = Inclusive 3.0,
+              consumer = Inclusive 2.0})
diff --git a/test/golden/common/pathItem/operation/parameters/allowEmptyValue/reset/report.md b/test/golden/common/pathItem/operation/parameters/allowEmptyValue/reset/report.md
new file mode 100644
index 0000000..1cb9137
--- /dev/null
+++ b/test/golden/common/pathItem/operation/parameters/allowEmptyValue/reset/report.md
@@ -0,0 +1,5 @@
+# **POST** /test
+
+## Parameter test1
+
+Expected that an empty parameter is allowed, but it isn't.
diff --git a/test/golden/common/pathItem/operation/parameters/allowEmptyValue/reset/trace-tree.yaml b/test/golden/common/pathItem/operation/parameters/allowEmptyValue/reset/trace-tree.yaml
index 9a0d1d9..52a0aff 100644
--- a/test/golden/common/pathItem/operation/parameters/allowEmptyValue/reset/trace-tree.yaml
+++ b/test/golden/common/pathItem/operation/parameters/allowEmptyValue/reset/trace-tree.yaml
@@ -1,4 +1,4 @@
 Left:
-  AtPath (ProdCons {producer = "/test", consumer = "/test"}):
+  AtPath "/test":
     InOperation PostMethod:
       InParam "test1": ParamEmptinessIncompatible
diff --git a/test/golden/common/pathItem/operation/parameters/allowEmptyValue/set/report.md b/test/golden/common/pathItem/operation/parameters/allowEmptyValue/set/report.md
new file mode 100644
index 0000000..4211f70
--- /dev/null
+++ b/test/golden/common/pathItem/operation/parameters/allowEmptyValue/set/report.md
@@ -0,0 +1 @@
+# No breaking changes found ✨
diff --git a/test/golden/common/pathItem/operation/parameters/change/report.md b/test/golden/common/pathItem/operation/parameters/change/report.md
new file mode 100644
index 0000000..c8bb963
--- /dev/null
+++ b/test/golden/common/pathItem/operation/parameters/change/report.md
@@ -0,0 +1,9 @@
+# **POST** /test
+
+## Parameter test
+
+### JSON Schema
+
+#### String
+
+Expected the type to be allowed, but it wasn't.
diff --git a/test/golden/common/pathItem/operation/parameters/change/trace-tree.yaml b/test/golden/common/pathItem/operation/parameters/change/trace-tree.yaml
index a385287..a2eb624 100644
--- a/test/golden/common/pathItem/operation/parameters/change/trace-tree.yaml
+++ b/test/golden/common/pathItem/operation/parameters/change/trace-tree.yaml
@@ -1,5 +1,5 @@
 Left:
-  AtPath (ProdCons {producer = "/test", consumer = "/test"}):
+  AtPath "/test":
     InOperation PostMethod:
       InParam "test":
         InParamSchema:
diff --git a/test/golden/common/pathItem/operation/parameters/required/false/add/report.md b/test/golden/common/pathItem/operation/parameters/required/false/add/report.md
new file mode 100644
index 0000000..4211f70
--- /dev/null
+++ b/test/golden/common/pathItem/operation/parameters/required/false/add/report.md
@@ -0,0 +1 @@
+# No breaking changes found ✨
diff --git a/test/golden/common/pathItem/operation/parameters/required/false/del/report.md b/test/golden/common/pathItem/operation/parameters/required/false/del/report.md
new file mode 100644
index 0000000..4211f70
--- /dev/null
+++ b/test/golden/common/pathItem/operation/parameters/required/false/del/report.md
@@ -0,0 +1 @@
+# No breaking changes found ✨
diff --git a/test/golden/common/pathItem/operation/parameters/required/reset/report.md b/test/golden/common/pathItem/operation/parameters/required/reset/report.md
new file mode 100644
index 0000000..4211f70
--- /dev/null
+++ b/test/golden/common/pathItem/operation/parameters/required/reset/report.md
@@ -0,0 +1 @@
+# No breaking changes found ✨
diff --git a/test/golden/common/pathItem/operation/parameters/required/set/report.md b/test/golden/common/pathItem/operation/parameters/required/set/report.md
new file mode 100644
index 0000000..fef9d52
--- /dev/null
+++ b/test/golden/common/pathItem/operation/parameters/required/set/report.md
@@ -0,0 +1,5 @@
+# **POST** /test
+
+## Parameter test1
+
+Expected the parameter to be optional, but it is required.
diff --git a/test/golden/common/pathItem/operation/parameters/required/set/trace-tree.yaml b/test/golden/common/pathItem/operation/parameters/required/set/trace-tree.yaml
index 5eee99d..e484608 100644
--- a/test/golden/common/pathItem/operation/parameters/required/set/trace-tree.yaml
+++ b/test/golden/common/pathItem/operation/parameters/required/set/trace-tree.yaml
@@ -1,4 +1,4 @@
 Left:
-  AtPath (ProdCons {producer = "/test", consumer = "/test"}):
+  AtPath "/test":
     InOperation PostMethod:
       InParam "test1": ParamRequired
diff --git a/test/golden/common/pathItem/operation/parameters/required/true/add/report.md b/test/golden/common/pathItem/operation/parameters/required/true/add/report.md
new file mode 100644
index 0000000..bad3c90
--- /dev/null
+++ b/test/golden/common/pathItem/operation/parameters/required/true/add/report.md
@@ -0,0 +1,3 @@
+# **POST** /test
+
+Parameter test2 is not supported.
diff --git a/test/golden/common/pathItem/operation/parameters/required/true/add/trace-tree.yaml b/test/golden/common/pathItem/operation/parameters/required/true/add/trace-tree.yaml
index df0067a..e4be5d6 100644
--- a/test/golden/common/pathItem/operation/parameters/required/true/add/trace-tree.yaml
+++ b/test/golden/common/pathItem/operation/parameters/required/true/add/trace-tree.yaml
@@ -1,3 +1,3 @@
 Left:
-  AtPath (ProdCons {producer = "/test", consumer = "/test"}):
+  AtPath "/test":
     InOperation PostMethod: ParamNotMatched "test2"
diff --git a/test/golden/common/pathItem/operation/parameters/required/true/del/report.md b/test/golden/common/pathItem/operation/parameters/required/true/del/report.md
new file mode 100644
index 0000000..4211f70
--- /dev/null
+++ b/test/golden/common/pathItem/operation/parameters/required/true/del/report.md
@@ -0,0 +1 @@
+# No breaking changes found ✨
diff --git a/test/golden/common/pathItem/operation/requestBody/mediaTypeObject/add/report.md b/test/golden/common/pathItem/operation/requestBody/mediaTypeObject/add/report.md
new file mode 100644
index 0000000..4211f70
--- /dev/null
+++ b/test/golden/common/pathItem/operation/requestBody/mediaTypeObject/add/report.md
@@ -0,0 +1 @@
+# No breaking changes found ✨
diff --git a/test/golden/common/pathItem/operation/requestBody/mediaTypeObject/change/report.md b/test/golden/common/pathItem/operation/requestBody/mediaTypeObject/change/report.md
new file mode 100644
index 0000000..637da11
--- /dev/null
+++ b/test/golden/common/pathItem/operation/requestBody/mediaTypeObject/change/report.md
@@ -0,0 +1,7 @@
+# **POST** /test
+
+## JSON Request
+
+### String
+
+Expected the type to be allowed, but it wasn't.
diff --git a/test/golden/common/pathItem/operation/requestBody/mediaTypeObject/change/trace-tree.yaml b/test/golden/common/pathItem/operation/requestBody/mediaTypeObject/change/trace-tree.yaml
index b247996..41b98f9 100644
--- a/test/golden/common/pathItem/operation/requestBody/mediaTypeObject/change/trace-tree.yaml
+++ b/test/golden/common/pathItem/operation/requestBody/mediaTypeObject/change/trace-tree.yaml
@@ -1,5 +1,5 @@
 Left:
-  AtPath (ProdCons {producer = "/test", consumer = "/test"}):
+  AtPath "/test":
     InOperation PostMethod:
       InRequest:
         InPayload:
diff --git a/test/golden/common/pathItem/operation/requestBody/mediaTypeObject/del/report.md b/test/golden/common/pathItem/operation/requestBody/mediaTypeObject/del/report.md
new file mode 100644
index 0000000..c0e06a4
--- /dev/null
+++ b/test/golden/common/pathItem/operation/requestBody/mediaTypeObject/del/report.md
@@ -0,0 +1,6 @@
+# **POST** /test
+
+## Request
+
+Couldn't find a request body for media type
+`application/x-www-form-urlencoded`.
diff --git a/test/golden/common/pathItem/operation/requestBody/mediaTypeObject/del/trace-tree.yaml b/test/golden/common/pathItem/operation/requestBody/mediaTypeObject/del/trace-tree.yaml
index b6f04b1..3b6684f 100644
--- a/test/golden/common/pathItem/operation/requestBody/mediaTypeObject/del/trace-tree.yaml
+++ b/test/golden/common/pathItem/operation/requestBody/mediaTypeObject/del/trace-tree.yaml
@@ -1,4 +1,4 @@
 Left:
-  AtPath (ProdCons {producer = "/test", consumer = "/test"}):
+  AtPath "/test":
     InOperation PostMethod:
       InRequest: RequestMediaTypeNotFound application/x-www-form-urlencoded
diff --git a/test/golden/common/pathItem/operation/requestBody/required/reset/report.md b/test/golden/common/pathItem/operation/requestBody/required/reset/report.md
new file mode 100644
index 0000000..4211f70
--- /dev/null
+++ b/test/golden/common/pathItem/operation/requestBody/required/reset/report.md
@@ -0,0 +1 @@
+# No breaking changes found ✨
diff --git a/test/golden/common/pathItem/operation/requestBody/required/set/report.md b/test/golden/common/pathItem/operation/requestBody/required/set/report.md
new file mode 100644
index 0000000..7e7677f
--- /dev/null
+++ b/test/golden/common/pathItem/operation/requestBody/required/set/report.md
@@ -0,0 +1,5 @@
+# **POST** /test
+
+## Request
+
+Expected the request body to be optional, but found it to be required.
diff --git a/test/golden/common/pathItem/operation/requestBody/required/set/trace-tree.yaml b/test/golden/common/pathItem/operation/requestBody/required/set/trace-tree.yaml
index fda0876..759e4f9 100644
--- a/test/golden/common/pathItem/operation/requestBody/required/set/trace-tree.yaml
+++ b/test/golden/common/pathItem/operation/requestBody/required/set/trace-tree.yaml
@@ -1,4 +1,4 @@
 Left:
-  AtPath (ProdCons {producer = "/test", consumer = "/test"}):
+  AtPath "/test":
     InOperation PostMethod:
       InRequest: RequestBodyRequired
diff --git a/test/golden/common/pathItem/operation/responses/add/report.md b/test/golden/common/pathItem/operation/responses/add/report.md
new file mode 100644
index 0000000..1e460e2
--- /dev/null
+++ b/test/golden/common/pathItem/operation/responses/add/report.md
@@ -0,0 +1,3 @@
+# **POST** /test
+
+Reponse code 500 is not supported.
diff --git a/test/golden/common/pathItem/operation/responses/add/trace-tree.yaml b/test/golden/common/pathItem/operation/responses/add/trace-tree.yaml
index 008b13e..ea7c116 100644
--- a/test/golden/common/pathItem/operation/responses/add/trace-tree.yaml
+++ b/test/golden/common/pathItem/operation/responses/add/trace-tree.yaml
@@ -1,3 +1,3 @@
 Left:
-  AtPath (ProdCons {producer = "/test", consumer = "/test"}):
+  AtPath "/test":
     InOperation PostMethod: ResponseCodeNotFound 500
diff --git a/test/golden/common/pathItem/operation/responses/change/headers/mandatory/add/report.md b/test/golden/common/pathItem/operation/responses/change/headers/mandatory/add/report.md
new file mode 100644
index 0000000..4211f70
--- /dev/null
+++ b/test/golden/common/pathItem/operation/responses/change/headers/mandatory/add/report.md
@@ -0,0 +1 @@
+# No breaking changes found ✨
diff --git a/test/golden/common/pathItem/operation/responses/change/headers/mandatory/del/report.md b/test/golden/common/pathItem/operation/responses/change/headers/mandatory/del/report.md
new file mode 100644
index 0000000..4b94b8a
--- /dev/null
+++ b/test/golden/common/pathItem/operation/responses/change/headers/mandatory/del/report.md
@@ -0,0 +1,5 @@
+# **POST** /test
+
+## Response code 200
+
+Couldn't find header `Test2`.
diff --git a/test/golden/common/pathItem/operation/responses/change/headers/mandatory/del/trace-tree.yaml b/test/golden/common/pathItem/operation/responses/change/headers/mandatory/del/trace-tree.yaml
index 48a7ea7..a8f6d76 100644
--- a/test/golden/common/pathItem/operation/responses/change/headers/mandatory/del/trace-tree.yaml
+++ b/test/golden/common/pathItem/operation/responses/change/headers/mandatory/del/trace-tree.yaml
@@ -1,4 +1,4 @@
 Left:
-  AtPath (ProdCons {producer = "/test", consumer = "/test"}):
+  AtPath "/test":
     InOperation PostMethod:
       WithStatusCode 200: ResponseHeaderMissing "Test2"
diff --git a/test/golden/common/pathItem/operation/responses/change/headers/optional/add/report.md b/test/golden/common/pathItem/operation/responses/change/headers/optional/add/report.md
new file mode 100644
index 0000000..4211f70
--- /dev/null
+++ b/test/golden/common/pathItem/operation/responses/change/headers/optional/add/report.md
@@ -0,0 +1 @@
+# No breaking changes found ✨
diff --git a/test/golden/common/pathItem/operation/responses/change/headers/optional/del/report.md b/test/golden/common/pathItem/operation/responses/change/headers/optional/del/report.md
new file mode 100644
index 0000000..4211f70
--- /dev/null
+++ b/test/golden/common/pathItem/operation/responses/change/headers/optional/del/report.md
@@ -0,0 +1 @@
+# No breaking changes found ✨
diff --git a/test/golden/common/pathItem/operation/responses/change/mediaTypeObject/add/report.md b/test/golden/common/pathItem/operation/responses/change/mediaTypeObject/add/report.md
new file mode 100644
index 0000000..98912fd
--- /dev/null
+++ b/test/golden/common/pathItem/operation/responses/change/mediaTypeObject/add/report.md
@@ -0,0 +1,6 @@
+# **POST** /test
+
+## Response code 200
+
+Couldn't find reponse for media type
+`application/x-www-form-urlencoded`.
diff --git a/test/golden/common/pathItem/operation/responses/change/mediaTypeObject/add/trace-tree.yaml b/test/golden/common/pathItem/operation/responses/change/mediaTypeObject/add/trace-tree.yaml
index d763c86..1051d3c 100644
--- a/test/golden/common/pathItem/operation/responses/change/mediaTypeObject/add/trace-tree.yaml
+++ b/test/golden/common/pathItem/operation/responses/change/mediaTypeObject/add/trace-tree.yaml
@@ -1,4 +1,4 @@
 Left:
-  AtPath (ProdCons {producer = "/test", consumer = "/test"}):
+  AtPath "/test":
     InOperation PostMethod:
       WithStatusCode 200: ResponseMediaTypeMissing application/x-www-form-urlencoded
diff --git a/test/golden/common/pathItem/operation/responses/change/mediaTypeObject/change/report.md b/test/golden/common/pathItem/operation/responses/change/mediaTypeObject/change/report.md
new file mode 100644
index 0000000..01bafbc
--- /dev/null
+++ b/test/golden/common/pathItem/operation/responses/change/mediaTypeObject/change/report.md
@@ -0,0 +1,7 @@
+# **POST** /test
+
+## JSON Response – 200
+
+### Number
+
+Expected the type to be allowed, but it wasn't.
diff --git a/test/golden/common/pathItem/operation/responses/change/mediaTypeObject/change/trace-tree.yaml b/test/golden/common/pathItem/operation/responses/change/mediaTypeObject/change/trace-tree.yaml
index 3e61526..051d29a 100644
--- a/test/golden/common/pathItem/operation/responses/change/mediaTypeObject/change/trace-tree.yaml
+++ b/test/golden/common/pathItem/operation/responses/change/mediaTypeObject/change/trace-tree.yaml
@@ -1,5 +1,5 @@
 Left:
-  AtPath (ProdCons {producer = "/test", consumer = "/test"}):
+  AtPath "/test":
     InOperation PostMethod:
       WithStatusCode 200:
         ResponsePayload:
diff --git a/test/golden/common/pathItem/operation/responses/change/mediaTypeObject/del/report.md b/test/golden/common/pathItem/operation/responses/change/mediaTypeObject/del/report.md
new file mode 100644
index 0000000..4211f70
--- /dev/null
+++ b/test/golden/common/pathItem/operation/responses/change/mediaTypeObject/del/report.md
@@ -0,0 +1 @@
+# No breaking changes found ✨
diff --git a/test/golden/common/pathItem/operation/responses/del/report.md b/test/golden/common/pathItem/operation/responses/del/report.md
new file mode 100644
index 0000000..4211f70
--- /dev/null
+++ b/test/golden/common/pathItem/operation/responses/del/report.md
@@ -0,0 +1 @@
+# No breaking changes found ✨
diff --git a/test/golden/common/property-removed/report.md b/test/golden/common/property-removed/report.md
new file mode 100644
index 0000000..17200d0
--- /dev/null
+++ b/test/golden/common/property-removed/report.md
@@ -0,0 +1,13 @@
+# **POST** /test
+
+## JSON Request
+
+### Object
+
+Expected the property `property2` to be allowed, but it wasn't.
+
+## JSON Response – 200
+
+### Object
+
+Don't have a required property `property2`.
diff --git a/test/golden/common/property-removed/trace-tree.yaml b/test/golden/common/property-removed/trace-tree.yaml
index daef57f..db439b7 100644
--- a/test/golden/common/property-removed/trace-tree.yaml
+++ b/test/golden/common/property-removed/trace-tree.yaml
@@ -1,5 +1,5 @@
 Left:
-  AtPath (ProdCons {producer = "/test", consumer = "/test"}):
+  AtPath "/test":
     InOperation PostMethod:
       InRequest:
         InPayload:
diff --git a/test/golden/common/property-required/report.md b/test/golden/common/property-required/report.md
new file mode 100644
index 0000000..5a87db2
--- /dev/null
+++ b/test/golden/common/property-required/report.md
@@ -0,0 +1,7 @@
+# **POST** /test
+
+## JSON Request
+
+### Object
+
+Don't have a required property `property2`.
diff --git a/test/golden/common/property-required/trace-tree.yaml b/test/golden/common/property-required/trace-tree.yaml
index 4f67b0f..10b4293 100644
--- a/test/golden/common/property-required/trace-tree.yaml
+++ b/test/golden/common/property-required/trace-tree.yaml
@@ -1,5 +1,5 @@
 Left:
-  AtPath (ProdCons {producer = "/test", consumer = "/test"}):
+  AtPath "/test":
     InOperation PostMethod:
       InRequest:
         InPayload:
diff --git a/test/golden/common/recursive/report.md b/test/golden/common/recursive/report.md
new file mode 100644
index 0000000..4211f70
--- /dev/null
+++ b/test/golden/common/recursive/report.md
@@ -0,0 +1 @@
+# No breaking changes found ✨
diff --git a/test/golden/common/security-scheme/report.md b/test/golden/common/security-scheme/report.md
new file mode 100644
index 0000000..f9f0d5f
--- /dev/null
+++ b/test/golden/common/security-scheme/report.md
@@ -0,0 +1,15 @@
+# **POST** /oauth/check
+
+## Security requirement 0
+
+### oauth
+
+Security scheme not met.
+
+# **GET** /oauth/sign\_out
+
+## Security requirement 1
+
+### oauth
+
+Security scheme not met.
diff --git a/test/golden/common/security-scheme/trace-tree.yaml b/test/golden/common/security-scheme/trace-tree.yaml
index 7d2c7d3..e2cc7ee 100644
--- a/test/golden/common/security-scheme/trace-tree.yaml
+++ b/test/golden/common/security-scheme/trace-tree.yaml
@@ -1,9 +1,9 @@
 Left:
-  AtPath (ProdCons {producer = "/oauth/check", consumer = "/oauth/check"}):
-    InOperation PostMethod:
-      SecurityRequirementStep 0:
-        SecuritySchemeStep "oauth": SecuritySchemeNotMatched
-  AtPath (ProdCons {producer = "/oauth/sign_out", consumer = "/oauth/sign_out"}):
+  AtPath "/oauth/sign_out":
     InOperation GetMethod:
       SecurityRequirementStep 1:
         SecuritySchemeStep "oauth": SecuritySchemeNotMatched
+  AtPath "/oauth/check":
+    InOperation PostMethod:
+      SecurityRequirementStep 0:
+        SecuritySchemeStep "oauth": SecuritySchemeNotMatched
diff --git a/test/golden/common/servers/report.md b/test/golden/common/servers/report.md
new file mode 100644
index 0000000..32d46b3
--- /dev/null
+++ b/test/golden/common/servers/report.md
@@ -0,0 +1,11 @@
+# **GET** /pets
+
+## Server `http://missing.url`
+
+Couldn't find a matching server.
+
+## Server `http://{x}variable.path/{y}/{openVariable1}/{openVariable2}`
+
+Enum value `a` is not supported.
+
+Expected a variable to be open (any value), but it wasn't.
diff --git a/test/golden/common/servers/trace-tree.yaml b/test/golden/common/servers/trace-tree.yaml
index a330b96..2b0d629 100644
--- a/test/golden/common/servers/trace-tree.yaml
+++ b/test/golden/common/servers/trace-tree.yaml
@@ -1,5 +1,5 @@
 Left:
-  AtPath (ProdCons {producer = "/pets", consumer = "/pets"}):
+  AtPath "/pets":
     InOperation GetMethod:
       InServer "http://{x}variable.path/{y}/{openVariable1}/{openVariable2}":
       - EnumValueNotConsumed 1 "a"
diff --git a/test/golden/common/unguarded-recursive/report.md b/test/golden/common/unguarded-recursive/report.md
new file mode 100644
index 0000000..21869f5
--- /dev/null
+++ b/test/golden/common/unguarded-recursive/report.md
@@ -0,0 +1,5 @@
+# **GET** /api/foo
+
+## JSON Response – 200
+
+Encountered recursion that is too complex for OpenApi Diff to untangle.
diff --git a/test/golden/common/unguarded-recursive/trace-tree.yaml b/test/golden/common/unguarded-recursive/trace-tree.yaml
index fa9f030..590caf5 100644
--- a/test/golden/common/unguarded-recursive/trace-tree.yaml
+++ b/test/golden/common/unguarded-recursive/trace-tree.yaml
@@ -1,5 +1,5 @@
 Left:
-  AtPath (ProdCons {producer = "/api/foo", consumer = "/api/foo"}):
+  AtPath "/api/foo":
     InOperation GetMethod:
       WithStatusCode 200:
         ResponsePayload: