diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,11 @@
 
 ## [Unreleased]
 
+## [1.3.0] - 2024-06-13
+
+### Changed
+- Simplify core API (breaking change) (#47)
+
 ## [1.2.0] - 2024-03-18
 
 ### Added
@@ -58,7 +63,8 @@
 - Extracted webgear-core from webgear-server
 - New arrow based API
 
-[Unreleased]: https://github.com/haskell-webgear/webgear/compare/v1.2.0...HEAD
+[Unreleased]: https://github.com/haskell-webgear/webgear/compare/v1.3.0...HEAD
+[1.3.0]: https://github.com/haskell-webgear/webgear/releases/tag/v1.3.0
 [1.2.0]: https://github.com/haskell-webgear/webgear/releases/tag/v1.2.0
 [1.1.1]: https://github.com/haskell-webgear/webgear/releases/tag/v1.1.1
 [1.1.0]: https://github.com/haskell-webgear/webgear/releases/tag/v1.1.0
diff --git a/src/WebGear/Core/Trait.hs b/src/WebGear/Core/Trait.hs
--- a/src/WebGear/Core/Trait.hs
+++ b/src/WebGear/Core/Trait.hs
@@ -3,11 +3,12 @@
 {- | Traits are optional attributes associated with a value. For
  example, a list containing totally ordered values might have a
  @Maximum@ trait where the associated attribute is the maximum
- value. This trait exists only if the list is non-empty. The 'Trait'
- typeclass provides an interface to extract such trait attributes.
+ value. This trait exists only if the list is non-empty.
 
  Traits help to associate attributes with values in a type-safe
- manner.
+ manner. WebGear associates traits with 'Request's and 'Response's to
+ ensure certian attributes are present in them and access those with
+ safety.
 
  Traits are somewhat similar to [refinement
  types](https://hackage.haskell.org/package/refined), but allow
@@ -45,8 +46,8 @@
 -}
 module WebGear.Core.Trait (
   -- * Core Types
-  Trait (..),
-  TraitAbsence (..),
+  Attribute,
+  Absence,
   Prerequisite,
   Get (..),
   Gets,
@@ -72,67 +73,67 @@
 import Data.Kind (Constraint, Type)
 import Data.Tagged (Tagged (..), untag)
 import GHC.TypeLits (ErrorMessage (..), TypeError)
+import WebGear.Core.Request (Request)
+import WebGear.Core.Response (Response)
 
--- | A trait is an attribute @t@ associated with a value @a@.
-class Trait (t :: Type) a where
-  -- | Type of the associated attribute when the trait holds for a
-  -- value
-  type Attribute t a :: Type
+{- | Type of the associated attribute when the trait @t@ holds for a
+   value @a@.
+-}
+type family Attribute t a :: Type
 
--- | A trait @t@ that can be retrieved from @a@ but could be absent.
-class (Trait t a) => TraitAbsence t a where
-  -- | Type that indicates that the trait does not exist for a
-  -- value. This could be an error message, exception etc.
-  type Absence t a :: Type
+{- | Type that indicates that the trait does not exist on a
+   request. This could be an error message, exception etc.
+-}
+type family Absence t :: Type
 
 {- | Indicates the constraints a trait depends upon as a
-prerequisite. This is used to assert that a trait @t@ can be
-extracted from a value @a@ only if one or more other traits are
-present in the trait list @ts@ associated with it.
+   prerequisite. This is used to assert that a trait @t@ can be
+   extracted from a request only if one or more other traits are
+   present in the trait list @ts@ associated with it.
 
-If a trait does not depend on other traits this can be set to the
-empty contraint @()@.
+   If a trait does not depend on other traits this can be set to the
+   empty contraint @()@.
 -}
-type family Prerequisite (t :: Type) (ts :: [Type]) (a :: Type) :: Constraint
+type family Prerequisite (t :: Type) (ts :: [Type]) :: Constraint
 
--- | Extract trait attributes from a value.
-class (Arrow h, TraitAbsence t a) => Get h t a where
-  -- | Attempt to witness the trait attribute from the value @a@.
+-- | Extract trait attributes from a request.
+class (Arrow h) => Get h t where
+  -- | Attempt to witness the trait attribute from the request.
   getTrait ::
-    (Prerequisite t ts a) =>
+    (Prerequisite t ts) =>
     -- | The trait to witness
     t ->
     -- | Arrow that attemtps to witness the trait and can possibly
     -- fail
-    h (a `With` ts) (Either (Absence t a) (Attribute t a))
+    h (Request `With` ts) (Either (Absence t) (Attribute t Request))
 
--- | Associate a trait attribute on a value
-class (Arrow h, Trait t a) => Set h (t :: Type) a where
-  -- | Set a trait attribute @t@ on the value @a \`With\` ts@.
+-- | Associate a trait attribute on a response
+class (Arrow h) => Set h (t :: Type) where
+  -- | Set a trait attribute @t@ on the value @Response \`With\` ts@.
   setTrait ::
     -- | The trait to set
     t ->
-    -- | A function to generate a witnessed value. This function must
-    -- be called by the `setTrait` implementation to generate a
-    -- witnessed value.
-    (a `With` ts -> a -> Attribute t a -> a `With` (t : ts)) ->
+    -- | A function to generate a witnessed response. This function
+    -- must be called by the `setTrait` implementation to generate a
+    -- witnessed response.
+    (Response `With` ts -> Response -> Attribute t Response -> Response `With` (t : ts)) ->
     -- | An arrow that attaches a new trait attribute to a witnessed
     -- value.
-    h (a `With` ts, Attribute t a) (a `With` (t : ts))
+    h (Response `With` ts, Attribute t Response) (Response `With` (t : ts))
 
-{- | @Gets h ts a@ is equivalent to @(Get h t1 a, Get h t2 a, ..., Get
- h tn a)@ where @ts = [t1, t2, ..., tn]@.
+{- | @Gets h ts@ is equivalent to @(Get h t1, Get h t2, ..., Get h tn)@
+ where @ts = [t1, t2, ..., tn]@.
 -}
-type family Gets h ts a :: Constraint where
-  Gets h '[] a = ()
-  Gets h (t : ts) a = (Get h t a, Gets h ts a)
+type family Gets h ts :: Constraint where
+  Gets h '[] = ()
+  Gets h (t : ts) = (Get h t, Gets h ts)
 
-{- | @Sets h ts a@ is equivalent to @(Set h t1 a, Set h t2 a, ..., Set
- h tn a)@ where @ts = [t1, t2, ..., tn]@.
+{- | @Sets h ts@ is equivalent to @(Set h t1, Set h t2, ..., Set h tn)@
+   where @ts = [t1, t2, ..., tn]@.
 -}
-type family Sets h ts a :: Constraint where
-  Sets h '[] a = ()
-  Sets h (t : ts) a = (Set h t a, Sets h ts a)
+type family Sets h ts :: Constraint where
+  Sets h '[] = ()
+  Sets h (t : ts) = (Set h t, Sets h ts)
 
 {- | A value associated with a list of traits, referred to as a
 witnessed value. Typically, this is used as an infix type constructor:
@@ -175,35 +176,35 @@
 wminus (With (_, rv) a) = With rv a
 {-# INLINE wminus #-}
 
-{- | Attempt to witness an additional trait with a witnessed value. This
- can fail indicating an 'Absence' of the trait.
+{- | Attempt to witness an additional trait with a witnessed
+   request. This can fail indicating an 'Absence' of the trait.
 -}
 probe ::
-  forall t ts h a.
-  (Get h t a, Prerequisite t ts a) =>
+  forall t ts h.
+  (Get h t, Prerequisite t ts) =>
   t ->
-  h (a `With` ts) (Either (Absence t a) (a `With` (t : ts)))
+  h (Request `With` ts) (Either (Absence t) (Request `With` (t : ts)))
 probe t = proc l -> do
   res <- getTrait t -< l
   arr add -< (l, res)
   where
-    add :: (a `With` ts, Either e (Attribute t a)) -> Either e (a `With` (t : ts))
+    add :: (Request `With` ts, Either e (Attribute t Request)) -> Either e (Request `With` (t : ts))
     add (_, Left e) = Left e
     add (With{..}, Right attr) = Right $ With{attribute = (attr, attribute), ..}
 {-# INLINE probe #-}
 
-{- | Set a trait attribute on witnessed value to produce another
-   witnessed value with the additional trait attached to it.
+{- | Set a trait attribute on witnessed response to produce another
+   witnessed response with the additional trait attached to it.
 -}
 plant ::
-  forall t ts h a.
-  (Set h t a) =>
+  forall t ts h.
+  (Set h t) =>
   t ->
-  h (a `With` ts, Attribute t a) (a `With` (t : ts))
+  h (Response `With` ts, Attribute t Response) (Response `With` (t : ts))
 plant t = proc (l, attr) -> do
   setTrait t add -< (l, attr)
   where
-    add :: a `With` ts -> a -> Attribute t a -> a `With` (t : ts)
+    add :: Response `With` ts -> Response -> Attribute t Response -> Response `With` (t : ts)
     add With{..} a' attr = With{attribute = (attr, attribute), unwitness = a'}
 {-# INLINE plant #-}
 
diff --git a/src/WebGear/Core/Trait/Auth/Basic.hs b/src/WebGear/Core/Trait/Auth/Basic.hs
--- a/src/WebGear/Core/Trait/Auth/Basic.hs
+++ b/src/WebGear/Core/Trait/Auth/Basic.hs
@@ -32,9 +32,14 @@
  authConfig :: 'BasicAuth' IO () 'Credentials'
  authConfig = 'BasicAuth'' { toBasicAttribute = pure . Right }
 
- type ErrorTraits = [Status, RequiredRequestHeader \"Content-Type\" Text, RequiredRequestHeader \"WWW-Authenticate\" Text, Body Text]
+ type ErrorTraits =
+  [ Status
+  , RequiredResponseHeader \"Content-Type\" Text
+  , RequiredResponseHeader \"WWW-Authenticate\" Text
+  , Body Text
+  ]
 
- errorHandler :: ('Handler' h IO, Sets h ErrorTraits Response)
+ errorHandler :: ('Handler' h IO, Sets h ErrorTraits)
               => h (Request \`With\` ts, 'BasicAuthError' e) Response
  errorHandler = 'respondUnauthorized' \"Basic\" \"MyRealm\"
  @
@@ -42,7 +47,7 @@
  we can add basic authentication to @myHandler@:
 
  @
- myHandlerWithAuth :: ('Handler' h IO, Get h ('BasicAuth' IO () 'Credentials') Request, Sets h ErrorTraits Response)
+ myHandlerWithAuth :: ('Handler' h IO, Get h ('BasicAuth' IO () 'Credentials'), Sets h ErrorTraits)
                    => 'RequestHandler' h ts
  myHandlerWithAuth = 'basicAuth' authConfig errorHandler myHandler
  @
@@ -124,29 +129,23 @@
   | BasicAuthAttributeError e
   deriving stock (Eq, Show, Read)
 
-instance Trait (BasicAuth' Required scheme m e a) Request where
-  type Attribute (BasicAuth' Required scheme m e a) Request = a
-
-instance TraitAbsence (BasicAuth' Required scheme m e a) Request where
-  type Absence (BasicAuth' Required scheme m e a) Request = BasicAuthError e
-
-instance Trait (BasicAuth' Optional scheme m e a) Request where
-  type Attribute (BasicAuth' Optional scheme m e a) Request = Either (BasicAuthError e) a
+type instance Attribute (BasicAuth' Required scheme m e a) Request = a
+type instance Absence (BasicAuth' Required scheme m e a) = BasicAuthError e
 
-instance TraitAbsence (BasicAuth' Optional scheme m e a) Request where
-  type Absence (BasicAuth' Optional scheme m e a) Request = Void
+type instance Attribute (BasicAuth' Optional scheme m e a) Request = Either (BasicAuthError e) a
+type instance Absence (BasicAuth' Optional scheme m e a) = Void
 
 type instance
-  Prerequisite (BasicAuth' x scheme m e a) ts Request =
+  Prerequisite (BasicAuth' x scheme m e a) ts =
     HasTrait (AuthorizationHeader scheme) ts
 
 basicAuthMiddleware ::
   ( ArrowChoice h
-  , Get h (BasicAuth' x scheme m e t) Request
+  , Get h (BasicAuth' x scheme m e t)
   , HasTrait (AuthorizationHeader scheme) ts
   ) =>
   BasicAuth' x scheme m e t ->
-  h (Request `With` ts, Absence (BasicAuth' x scheme m e t) Request) Response ->
+  h (Request `With` ts, Absence (BasicAuth' x scheme m e t)) Response ->
   Middleware h ts (BasicAuth' x scheme m e t : ts)
 basicAuthMiddleware authCfg errorHandler nextHandler =
   proc request -> do
@@ -169,7 +168,7 @@
 basicAuth ::
   forall m e t h ts.
   ( ArrowChoice h
-  , Get h (BasicAuth' Required "Basic" m e t) Request
+  , Get h (BasicAuth' Required "Basic" m e t)
   , HasTrait (AuthorizationHeader "Basic") ts
   ) =>
   -- | Authentication configuration
@@ -189,7 +188,7 @@
 basicAuth' ::
   forall scheme m e t h ts.
   ( ArrowChoice h
-  , Get h (BasicAuth' Required scheme m e t) Request
+  , Get h (BasicAuth' Required scheme m e t)
   , HasTrait (AuthorizationHeader scheme) ts
   ) =>
   -- | Authentication configuration
@@ -214,7 +213,7 @@
 optionalBasicAuth ::
   forall m e t h ts.
   ( ArrowChoice h
-  , Get h (BasicAuth' Optional "Basic" m e t) Request
+  , Get h (BasicAuth' Optional "Basic" m e t)
   , HasTrait (AuthorizationHeader "Basic") ts
   ) =>
   -- | Authentication configuration
@@ -233,7 +232,7 @@
 optionalBasicAuth' ::
   forall scheme m e t h ts.
   ( ArrowChoice h
-  , Get h (BasicAuth' Optional scheme m e t) Request
+  , Get h (BasicAuth' Optional scheme m e t)
   , HasTrait (AuthorizationHeader scheme) ts
   ) =>
   -- | Authentication configuration
diff --git a/src/WebGear/Core/Trait/Auth/Common.hs b/src/WebGear/Core/Trait/Auth/Common.hs
--- a/src/WebGear/Core/Trait/Auth/Common.hs
+++ b/src/WebGear/Core/Trait/Auth/Common.hs
@@ -72,7 +72,6 @@
       , RequiredResponseHeader "WWW-Authenticate" Text
       , Body PlainText Text
       ]
-      Response
   ) =>
   -- | The authentication scheme
   CI ByteString ->
diff --git a/src/WebGear/Core/Trait/Auth/JWT.hs b/src/WebGear/Core/Trait/Auth/JWT.hs
--- a/src/WebGear/Core/Trait/Auth/JWT.hs
+++ b/src/WebGear/Core/Trait/Auth/JWT.hs
@@ -36,9 +36,14 @@
    , toJWTAttribute = pure . Right
    }
 
- type ErrorTraits = [Status, RequiredRequestHeader \"Content-Type\" Text, RequiredRequestHeader \"WWW-Authenticate\" Text, Body Text]
+ type ErrorTraits =
+  [ Status
+  , RequiredResponseHeader \"Content-Type\" Text
+  , RequiredResponseHeader \"WWW-Authenticate\" Text
+  , Body Text
+  ]
 
- errorHandler :: ('Handler' h IO, Sets h ErrorTraits Response)
+ errorHandler :: ('Handler' h IO, Sets h ErrorTraits)
               => h (Request \`With\` ts, 'JWTAuthError' e) Response
  errorHandler = 'respondUnauthorized' \"Bearer\" \"MyRealm\"
  @
@@ -46,7 +51,7 @@
  we can add JWT authentication to @myHandler@:
 
  @
- myHandlerWithAuth :: ('Handler' h IO, Get h ('JWTAuth' IO () 'JWT.ClaimsSet') Request, Sets h ErrorTraits Response)
+ myHandlerWithAuth :: ('Handler' h IO, Get h ('JWTAuth' IO () 'JWT.ClaimsSet'), Sets h ErrorTraits)
                    => 'RequestHandler' h ts
  myHandlerWithAuth = 'jwtAuth' authConfig errorHandler myHandler
  @
@@ -116,20 +121,14 @@
   | JWTAuthAttributeError e
   deriving stock (Eq, Show)
 
-instance Trait (JWTAuth' Required scheme m e a) Request where
-  type Attribute (JWTAuth' Required scheme m e a) Request = a
-
-instance TraitAbsence (JWTAuth' Required scheme m e a) Request where
-  type Absence (JWTAuth' Required scheme m e a) Request = JWTAuthError e
-
-instance Trait (JWTAuth' Optional scheme m e a) Request where
-  type Attribute (JWTAuth' Optional scheme m e a) Request = Either (JWTAuthError e) a
+type instance Attribute (JWTAuth' Required scheme m e a) Request = a
+type instance Absence (JWTAuth' Required scheme m e a) = JWTAuthError e
 
-instance TraitAbsence (JWTAuth' Optional scheme m e a) Request where
-  type Absence (JWTAuth' Optional scheme m e a) Request = Void
+type instance Attribute (JWTAuth' Optional scheme m e a) Request = Either (JWTAuthError e) a
+type instance Absence (JWTAuth' Optional scheme m e a) = Void
 
 type instance
-  Prerequisite (JWTAuth' x scheme m e a) ts Request =
+  Prerequisite (JWTAuth' x scheme m e a) ts =
     HasTrait (AuthorizationHeader scheme) ts
 
 {- | Middleware to add JWT authentication protection for a
@@ -148,7 +147,7 @@
 -}
 jwtAuth ::
   ( ArrowChoice h
-  , Get h (JWTAuth m e t) Request
+  , Get h (JWTAuth m e t)
   , HasTrait (AuthorizationHeader "Bearer") ts
   ) =>
   -- | Authentication configuration
@@ -176,7 +175,7 @@
 -}
 optionalJWTAuth ::
   ( ArrowChoice h
-  , Get h (JWTAuth' Optional "Bearer" m e t) Request
+  , Get h (JWTAuth' Optional "Bearer" m e t)
   , HasTrait (AuthorizationHeader "Bearer") ts
   ) =>
   -- | Authentication configuration
@@ -188,11 +187,11 @@
 jwtAuthMiddleware ::
   forall scheme e t x h m ts.
   ( ArrowChoice h
-  , Get h (JWTAuth' x scheme m e t) Request
+  , Get h (JWTAuth' x scheme m e t)
   , HasTrait (AuthorizationHeader scheme) ts
   ) =>
   JWTAuth' x scheme m e t ->
-  h (Request `With` ts, Absence (JWTAuth' x scheme m e t) Request) Response ->
+  h (Request `With` ts, Absence (JWTAuth' x scheme m e t)) Response ->
   Middleware h ts (JWTAuth' x scheme m e t : ts)
 jwtAuthMiddleware authCfg errorHandler nextHandler =
   proc request -> do
@@ -219,7 +218,7 @@
 jwtAuth' ::
   forall scheme e t h m ts.
   ( ArrowChoice h
-  , Get h (JWTAuth' Required scheme m e t) Request
+  , Get h (JWTAuth' Required scheme m e t)
   , HasTrait (AuthorizationHeader scheme) ts
   ) =>
   -- | Authentication configuration
@@ -248,7 +247,7 @@
 optionalJWTAuth' ::
   forall scheme e t h m ts.
   ( ArrowChoice h
-  , Get h (JWTAuth' Optional scheme m e t) Request
+  , Get h (JWTAuth' Optional scheme m e t)
   , HasTrait (AuthorizationHeader scheme) ts
   ) =>
   -- | Authentication configuration
diff --git a/src/WebGear/Core/Trait/Body.hs b/src/WebGear/Core/Trait/Body.hs
--- a/src/WebGear/Core/Trait/Body.hs
+++ b/src/WebGear/Core/Trait/Body.hs
@@ -1,17 +1,17 @@
 {- | Traits and middlewares to handle request and response body
    payloads.
 
- The 'requestBody' middleware attempts to convert the body to a
- Haskell value or invoke an error handler if that fails.
+   The 'requestBody' middleware attempts to convert the body to a
+   Haskell value or invoke an error handler if that fails.
 
- The 'respondA' middleware generates a response from an HTTP status
- and a response body.
+   The 'respondA' middleware generates a response from an HTTP status
+   and a response body.
 
- If you need finer control over setting the body, use 'setBody' or
- 'setBodyWithoutContentType'. These arrows accept a witnessed response
- and a body and sets the body in the response. You can generate an
- input response object using functions from
- "WebGear.Core.Trait.Status" module.
+   If you need finer control over setting the body, use 'setBody' or
+   'setBodyWithoutContentType'. These arrows accept a witnessed
+   response and a body and sets the body in the response. You can
+   generate an input response object using functions from
+   "WebGear.Core.Trait.Status" module.
 -}
 module WebGear.Core.Trait.Body (
   -- * Traits
@@ -36,12 +36,12 @@
 import WebGear.Core.Request (Request)
 import WebGear.Core.Response (Response, ResponseBody)
 import WebGear.Core.Trait (
+  Absence,
+  Attribute,
   Get,
   Prerequisite,
   Set,
   Sets,
-  Trait (..),
-  TraitAbsence (..),
   With (..),
   plant,
   probe,
@@ -52,22 +52,16 @@
 -- | Request or response body with MIME types @mimeTypes@ and type @t@.
 newtype Body (mimeType :: Type) (t :: Type) = Body mimeType
 
-instance Trait (Body mt t) Request where
-  type Attribute (Body mt t) Request = t
-
-instance TraitAbsence (Body mt t) Request where
-  type Absence (Body mt t) Request = Text
-
-type instance Prerequisite (Body mt t) ts Request = ()
+type instance Attribute (Body mt t) Request = t
+type instance Absence (Body mt t) = Text
+type instance Prerequisite (Body mt t) ts = ()
 
-instance Trait (Body mt t) Response where
-  type Attribute (Body mt t) Response = t
+type instance Attribute (Body mt t) Response = t
 
 -- | Type representing responses without a statically known MIME type
 data UnknownContentBody = UnknownContentBody
 
-instance Trait UnknownContentBody Response where
-  type Attribute UnknownContentBody Response = ResponseBody
+type instance Attribute UnknownContentBody Response = ResponseBody
 
 {- | Middleware to extract a request body.
 
@@ -83,7 +77,7 @@
 requestBody ::
   forall t mt h m ts.
   ( Handler h m
-  , Get h (Body mt t) Request
+  , Get h (Body mt t)
   ) =>
   mt ->
   -- | Error handler in case body cannot be retrieved
@@ -110,7 +104,7 @@
 -}
 setBody ::
   forall body mt h ts.
-  ( Sets h [Body mt body, RequiredResponseHeader "Content-Type" Text] Response
+  ( Sets h [Body mt body, RequiredResponseHeader "Content-Type" Text]
   , MIMEType mt
   ) =>
   mt ->
@@ -132,7 +126,7 @@
 -}
 setBodyWithoutContentType ::
   forall h ts.
-  (Set h UnknownContentBody Response) =>
+  (Set h UnknownContentBody) =>
   h (Response `With` ts, ResponseBody) (Response `With` (UnknownContentBody : ts))
 setBodyWithoutContentType = plant UnknownContentBody
 {-# INLINE setBodyWithoutContentType #-}
@@ -151,7 +145,7 @@
 respondA ::
   forall body mt h m.
   ( Handler h m
-  , Sets h [Status, Body mt body, RequiredResponseHeader "Content-Type" Text] Response
+  , Sets h [Status, Body mt body, RequiredResponseHeader "Content-Type" Text]
   , MIMEType mt
   ) =>
   -- | Response status
diff --git a/src/WebGear/Core/Trait/Cookie.hs b/src/WebGear/Core/Trait/Cookie.hs
--- a/src/WebGear/Core/Trait/Cookie.hs
+++ b/src/WebGear/Core/Trait/Cookie.hs
@@ -23,12 +23,12 @@
 import WebGear.Core.Request (Request)
 import WebGear.Core.Response (Response)
 import WebGear.Core.Trait (
+  Absence,
+  Attribute,
   Get,
   HasTrait,
   Prerequisite,
   Set,
-  Trait (..),
-  TraitAbsence (..),
   With,
   plant,
   probe,
@@ -46,30 +46,23 @@
 -- | Trait for a cookie in HTTP requests
 data Cookie (e :: Existence) (name :: Symbol) (val :: Type) = Cookie
 
-instance Trait (Cookie Required name val) Request where
-  type Attribute (Cookie Required name val) Request = val
-
+type instance Attribute (Cookie Required name val) Request = val
+type instance Absence (Cookie Required name val) = Either CookieNotFound CookieParseError
 type instance
-  Prerequisite (Cookie e name val) ts Request =
+  Prerequisite (Cookie e name val) ts =
     HasTrait (RequestHeader e Strict "Cookie" Text) ts
 
-instance TraitAbsence (Cookie Required name val) Request where
-  type Absence (Cookie Required name val) Request = Either CookieNotFound CookieParseError
-
-instance Trait (Cookie Optional name val) Request where
-  type Attribute (Cookie Optional name val) Request = Maybe val
-
-instance TraitAbsence (Cookie Optional name val) Request where
-  type Absence (Cookie Optional name val) Request = CookieParseError
+type instance Attribute (Cookie Optional name val) Request = Maybe val
+type instance Absence (Cookie Optional name val) = CookieParseError
 
 cookieHandler ::
   forall name val e h ts.
   ( ArrowChoice h
-  , Get h (Cookie e name val) Request
+  , Get h (Cookie e name val)
   , HasTrait (RequestHeader e Strict "Cookie" Text) ts
   ) =>
   -- | error handler
-  h (Request `With` ts, Absence (Cookie e name val) Request) Response ->
+  h (Request `With` ts, Absence (Cookie e name val)) Response ->
   Middleware h ts (Cookie e name val : ts)
 cookieHandler errorHandler nextHandler = proc request -> do
   result <- probe Cookie -< request
@@ -89,7 +82,7 @@
 cookie ::
   forall name val h ts.
   ( ArrowChoice h
-  , Get h (Cookie Required name val) Request
+  , Get h (Cookie Required name val)
   , HasTrait (RequestHeader Required Strict "Cookie" Text) ts
   ) =>
   -- | Error handler
@@ -110,7 +103,7 @@
 optionalCookie ::
   forall name val h ts.
   ( ArrowChoice h
-  , Get h (Cookie Optional name val) Request
+  , Get h (Cookie Optional name val)
   , HasTrait (RequestHeader Optional Strict "Cookie" Text) ts
   ) =>
   -- | Error handler
@@ -122,11 +115,9 @@
 -- | Trait for a cookie in HTTP responses
 data SetCookie (e :: Existence) (name :: Symbol) = SetCookie
 
-instance Trait (SetCookie Required name) Response where
-  type Attribute (SetCookie Required name) Response = Cookie.SetCookie
+type instance Attribute (SetCookie Required name) Response = Cookie.SetCookie
 
-instance Trait (SetCookie Optional name) Response where
-  type Attribute (SetCookie Optional name) Response = Maybe Cookie.SetCookie
+type instance Attribute (SetCookie Optional name) Response = Maybe Cookie.SetCookie
 
 {- | Set a cookie value in a response.
 
@@ -136,7 +127,7 @@
 -}
 setCookie ::
   forall name h ts.
-  (Set h (SetCookie Required name) Response) =>
+  (Set h (SetCookie Required name)) =>
   h (Response `With` ts, Cookie.SetCookie) (Response `With` (SetCookie Required name : ts))
 setCookie = plant SetCookie
 {-# INLINE setCookie #-}
@@ -153,7 +144,7 @@
 -}
 setOptionalCookie ::
   forall name h ts.
-  (Set h (SetCookie Optional name) Response) =>
+  (Set h (SetCookie Optional name)) =>
   h (Response `With` ts, Maybe Cookie.SetCookie) (Response `With` (SetCookie Optional name : ts))
 setOptionalCookie = plant SetCookie
 {-# INLINE setOptionalCookie #-}
diff --git a/src/WebGear/Core/Trait/Header.hs b/src/WebGear/Core/Trait/Header.hs
--- a/src/WebGear/Core/Trait/Header.hs
+++ b/src/WebGear/Core/Trait/Header.hs
@@ -61,11 +61,11 @@
 import WebGear.Core.Request (Request, requestHeader)
 import WebGear.Core.Response (Response)
 import WebGear.Core.Trait (
+  Absence,
+  Attribute,
   Get (..),
   Prerequisite,
   Set,
-  Trait (..),
-  TraitAbsence (..),
   With,
   plant,
   probe,
@@ -80,10 +80,10 @@
 newtype HeaderParseError = HeaderParseError Text
   deriving stock (Read, Show, Eq)
 
-{- | A 'Trait' for capturing an HTTP header of specified @name@ and
- converting it to some type @val@. The modifiers @e@ and @p@ determine
- how missing headers and parsing errors are handled. The header name
- is compared case-insensitively.
+{- | A trait for capturing an HTTP request header of specified @name@
+ and converting it to some type @val@. The modifiers @e@ and @p@
+ determine how the missing headers and parsing errors are handled. The
+ header name is compared case-insensitively.
 -}
 data RequestHeader (e :: Existence) (p :: ParseStyle) (name :: Symbol) (val :: Type) = RequestHeader
 
@@ -93,37 +93,25 @@
 -- | A `RequestHeader` that is optional and parsed strictly
 type OptionalRequestHeader = RequestHeader Optional Strict
 
-instance Trait (RequestHeader Required Strict name val) Request where
-  type Attribute (RequestHeader Required Strict name val) Request = val
-
-instance TraitAbsence (RequestHeader Required Strict name val) Request where
-  type Absence (RequestHeader Required Strict name val) Request = Either HeaderNotFound HeaderParseError
-
-instance Trait (RequestHeader Optional Strict name val) Request where
-  type Attribute (RequestHeader Optional Strict name val) Request = Maybe val
-
-instance TraitAbsence (RequestHeader Optional Strict name val) Request where
-  type Absence (RequestHeader Optional Strict name val) Request = HeaderParseError
-
-instance Trait (RequestHeader Required Lenient name val) Request where
-  type Attribute (RequestHeader Required Lenient name val) Request = Either Text val
+type instance Attribute (RequestHeader Required Strict name val) Request = val
+type instance Absence (RequestHeader Required Strict name val) = Either HeaderNotFound HeaderParseError
 
-instance TraitAbsence (RequestHeader Required Lenient name val) Request where
-  type Absence (RequestHeader Required Lenient name val) Request = HeaderNotFound
+type instance Attribute (RequestHeader Optional Strict name val) Request = Maybe val
+type instance Absence (RequestHeader Optional Strict name val) = HeaderParseError
 
-instance Trait (RequestHeader Optional Lenient name val) Request where
-  type Attribute (RequestHeader Optional Lenient name val) Request = Maybe (Either Text val)
+type instance Attribute (RequestHeader Required Lenient name val) Request = Either Text val
+type instance Absence (RequestHeader Required Lenient name val) = HeaderNotFound
 
-instance TraitAbsence (RequestHeader Optional Lenient name val) Request where
-  type Absence (RequestHeader Optional Lenient name val) Request = Void
+type instance Attribute (RequestHeader Optional Lenient name val) Request = Maybe (Either Text val)
+type instance Absence (RequestHeader Optional Lenient name val) = Void
 
-type instance Prerequisite (RequestHeader e p name val) ts Request = ()
+type instance Prerequisite (RequestHeader e p name val) ts = ()
 
 headerHandler ::
   forall name val e p h ts.
-  (Get h (RequestHeader e p name val) Request, ArrowChoice h) =>
+  (Get h (RequestHeader e p name val), ArrowChoice h) =>
   -- | error handler
-  h (Request `With` ts, Absence (RequestHeader e p name val) Request) Response ->
+  h (Request `With` ts, Absence (RequestHeader e p name val)) Response ->
   Middleware h ts (RequestHeader e p name val : ts)
 headerHandler errorHandler nextHandler = proc request -> do
   result <- probe RequestHeader -< request
@@ -132,79 +120,82 @@
     Right val -> nextHandler -< val
 {-# INLINE headerHandler #-}
 
-{- | Extract a header value and convert it to a value of type @val@.
+{- | Extract a request header value and convert it to a value of type
+   @val@.
 
- The associated trait attribute has type @val@.
+   The associated trait attribute has type @val@.
 
- Example usage:
+   Example usage:
 
- > header @"Content-Length" @Integer errorHandler okHandler
+   > header @"Content-Length" @Integer errorHandler okHandler
 -}
 header ::
   forall name val h ts.
-  (Get h (RequestHeader Required Strict name val) Request, ArrowChoice h) =>
+  (Get h (RequestHeader Required Strict name val), ArrowChoice h) =>
   -- | Error handler
   h (Request `With` ts, Either HeaderNotFound HeaderParseError) Response ->
   Middleware h ts (RequestHeader Required Strict name val : ts)
 header = headerHandler
 {-# INLINE header #-}
 
-{- | Extract an optional header value and convert it to a value of type
- @val@.
+{- | Extract an optional request header value and convert it to a value
+   of type @val@.
 
- The associated trait attribute has type @Maybe val@; a @Nothing@
- value indicates that the header is missing from the request.
+   The associated trait attribute has type @Maybe val@; a @Nothing@
+   value indicates that the header is missing from the request.
 
- Example usage:
+   Example usage:
 
- > optionalHeader @"Content-Length" @Integer errorHandler okHandler
+   > optionalHeader @"Content-Length" @Integer errorHandler okHandler
 -}
 optionalHeader ::
   forall name val h ts.
-  (Get h (RequestHeader Optional Strict name val) Request, ArrowChoice h) =>
+  (Get h (RequestHeader Optional Strict name val), ArrowChoice h) =>
   -- | Error handler
   h (Request `With` ts, HeaderParseError) Response ->
   Middleware h ts (RequestHeader Optional Strict name val : ts)
 optionalHeader = headerHandler
 {-# INLINE optionalHeader #-}
 
-{- | Extract a header value and convert it to a value of type @val@.
+{- | Extract a request header value and convert it to a value of type
+   @val@.
 
- The associated trait attribute has type @Either Text val@. The
- parsing is done leniently and any errors are reported in the trait
- attribute.
+   The associated trait attribute has type @Either Text val@. The
+   parsing is done leniently and any errors are reported in the trait
+   attribute.
 
- Example usage:
+   Example usage:
 
- > lenientHeader @"Content-Length" @Integer errorHandler okHandler
+   > lenientHeader @"Content-Length" @Integer errorHandler okHandler
 -}
 lenientHeader ::
   forall name val h ts.
-  (Get h (RequestHeader Required Lenient name val) Request, ArrowChoice h) =>
+  (Get h (RequestHeader Required Lenient name val), ArrowChoice h) =>
   -- | Error handler
   h (Request `With` ts, HeaderNotFound) Response ->
   Middleware h ts (RequestHeader Required Lenient name val : ts)
 lenientHeader = headerHandler
 {-# INLINE lenientHeader #-}
 
-{- | Extract a header value and convert it to a value of type @val@.
+{- | Extract a request header value and convert it to a value of type
+   @val@.
 
- The associated trait attribute has type @Maybe (Either Text
- val)@. The parsing is done leniently. Any parsing errors and
- missing header are reported in the trait attribute.
+   The associated trait attribute has type @Maybe (Either Text
+   val)@. The parsing is done leniently. Any parsing errors and
+   missing header are reported in the trait attribute.
 
- Example usage:
+   Example usage:
 
- > optionalLenientHeader @"Content-Length" @Integer handler
+   > optionalLenientHeader @"Content-Length" @Integer handler
 -}
 optionalLenientHeader ::
   forall name val h ts.
-  (Get h (RequestHeader Optional Lenient name val) Request, ArrowChoice h) =>
+  (Get h (RequestHeader Optional Lenient name val), ArrowChoice h) =>
   Middleware h ts (RequestHeader Optional Lenient name val : ts)
 optionalLenientHeader = headerHandler $ arr (absurd . snd)
 {-# INLINE optionalLenientHeader #-}
 
-{- | A 'Trait' for setting a header in the HTTP response. It has a
+{- | A trait for setting a header in the HTTP response. It has a
  specified @name@ and a value of type @val@. The header name is
  compared case-insensitively. The modifier @e@ determines whether the
  header is mandatory or optional.
@@ -217,11 +208,9 @@
 -- | A `ResponseHeader` that is optional
 type OptionalResponseHeader = ResponseHeader Optional
 
-instance Trait (ResponseHeader Required name val) Response where
-  type Attribute (ResponseHeader Required name val) Response = val
+type instance Attribute (ResponseHeader Required name val) Response = val
 
-instance Trait (ResponseHeader Optional name val) Response where
-  type Attribute (ResponseHeader Optional name val) Response = Maybe val
+type instance Attribute (ResponseHeader Optional name val) Response = Maybe val
 
 {- | Set a header value in a response.
 
@@ -231,7 +220,7 @@
 -}
 setHeader ::
   forall name val h ts.
-  (Set h (ResponseHeader Required name val) Response) =>
+  (Set h (ResponseHeader Required name val)) =>
   h (Response `With` ts, val) (Response `With` (ResponseHeader Required name val : ts))
 setHeader = plant ResponseHeader
 {-# INLINE setHeader #-}
@@ -248,7 +237,7 @@
 -}
 setOptionalHeader ::
   forall name val h ts.
-  (Set h (ResponseHeader Optional name val) Response) =>
+  (Set h (ResponseHeader Optional name val)) =>
   h (Response `With` ts, Maybe val) (Response `With` (ResponseHeader Optional name val : ts))
 setOptionalHeader = plant ResponseHeader
 {-# INLINE setOptionalHeader #-}
diff --git a/src/WebGear/Core/Trait/Method.hs b/src/WebGear/Core/Trait/Method.hs
--- a/src/WebGear/Core/Trait/Method.hs
+++ b/src/WebGear/Core/Trait/Method.hs
@@ -10,9 +10,9 @@
 import qualified Network.HTTP.Types as HTTP
 import WebGear.Core.Handler (Middleware, RouteMismatch, routeMismatch)
 import WebGear.Core.Request (Request)
-import WebGear.Core.Trait (Get (..), Prerequisite, Trait (..), TraitAbsence (..), probe)
+import WebGear.Core.Trait (Absence, Attribute, Get (..), Prerequisite, probe)
 
--- | A 'Trait' for capturing the HTTP method of a request
+-- | A trait for capturing the HTTP method of a request
 newtype Method = Method HTTP.StdMethod
 
 -- | Failure to match method against an expected value
@@ -21,13 +21,9 @@
   , actualMethod :: HTTP.Method
   }
 
-instance Trait Method Request where
-  type Attribute Method Request = HTTP.StdMethod
-
-instance TraitAbsence Method Request where
-  type Absence Method Request = MethodMismatch
-
-type instance Prerequisite Method ts Request = ()
+type instance Attribute Method Request = HTTP.StdMethod
+type instance Absence Method = MethodMismatch
+type instance Prerequisite Method ts = ()
 
 {- | Check whether the request has a specified HTTP method.
 
@@ -43,7 +39,7 @@
  cases where both an HTTP method and a path need to be matched.
 -}
 method ::
-  (Get h Method Request, ArrowChoice h, ArrowError RouteMismatch h) =>
+  (Get h Method, ArrowChoice h, ArrowError RouteMismatch h) =>
   HTTP.StdMethod ->
   Middleware h ts (Method : ts)
 method m nextHandler = probe (Method m) >>> routeMismatch ||| nextHandler
diff --git a/src/WebGear/Core/Trait/Path.hs b/src/WebGear/Core/Trait/Path.hs
--- a/src/WebGear/Core/Trait/Path.hs
+++ b/src/WebGear/Core/Trait/Path.hs
@@ -29,7 +29,7 @@
 import Language.Haskell.TH.Syntax (Exp (..), Lit (..), Q, TyLit (StrTyLit), Type (..), mkName)
 import WebGear.Core.Handler (Middleware, RouteMismatch, routeMismatch)
 import WebGear.Core.Request (Request)
-import WebGear.Core.Trait (Get, Prerequisite, Trait (..), TraitAbsence (..), probe)
+import WebGear.Core.Trait (Absence, Attribute, Get, Prerequisite, probe)
 import WebGear.Core.Trait.Method (method)
 import Prelude hiding (drop, filter, take)
 
@@ -38,13 +38,9 @@
 -}
 newtype Path = Path Text
 
-instance Trait Path Request where
-  type Attribute Path Request = ()
-
-instance TraitAbsence Path Request where
-  type Absence Path Request = ()
-
-type instance Prerequisite Path ts Request = ()
+type instance Attribute Path Request = ()
+type instance Absence Path = ()
+type instance Prerequisite Path ts = ()
 
 {- | A path variable that is extracted and converted to a value of
  type @val@. The @tag@ is usually a type-level symbol (string) to
@@ -56,24 +52,16 @@
 data PathVarError = PathVarNotFound | PathVarParseError Text
   deriving stock (Eq, Show, Read)
 
-instance Trait (PathVar tag val) Request where
-  type Attribute (PathVar tag val) Request = val
-
-instance TraitAbsence (PathVar tag val) Request where
-  type Absence (PathVar tag val) Request = PathVarError
-
-type instance Prerequisite (PathVar tag val) ts Request = ()
+type instance Attribute (PathVar tag val) Request = val
+type instance Absence (PathVar tag val) = PathVarError
+type instance Prerequisite (PathVar tag val) ts = ()
 
 -- | Trait to indicate that no more path components are present in the request
 data PathEnd = PathEnd
 
-instance Trait PathEnd Request where
-  type Attribute PathEnd Request = ()
-
-instance TraitAbsence PathEnd Request where
-  type Absence PathEnd Request = ()
-
-type instance Prerequisite PathEnd ts Request = ()
+type instance Attribute PathEnd Request = ()
+type instance Absence PathEnd = ()
+type instance Prerequisite PathEnd ts = ()
 
 {- | A middleware that literally matches path @s@.
 
@@ -87,7 +75,7 @@
  > path "a/b/c" handler
 -}
 path ::
-  (Get h Path Request, ArrowChoice h, ArrowError RouteMismatch h) =>
+  (Get h Path, ArrowChoice h, ArrowError RouteMismatch h) =>
   Text ->
   Middleware h ts (Path : ts)
 path s nextHandler = probe (Path s) >>> routeMismatch ||| nextHandler
@@ -107,14 +95,14 @@
 -}
 pathVar ::
   forall tag val h ts.
-  (Get h (PathVar tag val) Request, ArrowChoice h, ArrowError RouteMismatch h) =>
+  (Get h (PathVar tag val), ArrowChoice h, ArrowError RouteMismatch h) =>
   Middleware h ts (PathVar tag val : ts)
 pathVar nextHandler = probe PathVar >>> routeMismatch ||| nextHandler
 {-# INLINE pathVar #-}
 
 -- | A middleware that verifies that end of path is reached.
 pathEnd ::
-  (Get h PathEnd Request, ArrowChoice h, ArrowError RouteMismatch h) =>
+  (Get h PathEnd, ArrowChoice h, ArrowError RouteMismatch h) =>
   Middleware h ts (PathEnd : ts)
 pathEnd nextHandler = probe PathEnd >>> routeMismatch ||| nextHandler
 {-# INLINE pathEnd #-}
diff --git a/src/WebGear/Core/Trait/QueryParam.hs b/src/WebGear/Core/Trait/QueryParam.hs
--- a/src/WebGear/Core/Trait/QueryParam.hs
+++ b/src/WebGear/Core/Trait/QueryParam.hs
@@ -43,7 +43,7 @@
 import WebGear.Core.Modifiers (Existence (..), ParseStyle (..))
 import WebGear.Core.Request (Request)
 import WebGear.Core.Response (Response)
-import WebGear.Core.Trait (Get, Prerequisite, Trait (..), TraitAbsence (..), With, probe)
+import WebGear.Core.Trait (Absence, Attribute, Get, Prerequisite, With, probe)
 
 {- | Capture a query parameter with a specified @name@ and convert it to
  a value of type @val@. The type parameter @e@ denotes whether the
@@ -67,36 +67,24 @@
 newtype ParamParseError = ParamParseError Text
   deriving stock (Read, Show, Eq)
 
-instance Trait (QueryParam Required Strict name val) Request where
-  type Attribute (QueryParam Required Strict name val) Request = val
-
-instance TraitAbsence (QueryParam Required Strict name val) Request where
-  type Absence (QueryParam Required Strict name val) Request = Either ParamNotFound ParamParseError
-
-instance Trait (QueryParam Optional Strict name val) Request where
-  type Attribute (QueryParam Optional Strict name val) Request = Maybe val
-
-instance TraitAbsence (QueryParam Optional Strict name val) Request where
-  type Absence (QueryParam Optional Strict name val) Request = ParamParseError
-
-instance Trait (QueryParam Required Lenient name val) Request where
-  type Attribute (QueryParam Required Lenient name val) Request = Either Text val
+type instance Attribute (QueryParam Required Strict name val) Request = val
+type instance Absence (QueryParam Required Strict name val) = Either ParamNotFound ParamParseError
 
-instance TraitAbsence (QueryParam Required Lenient name val) Request where
-  type Absence (QueryParam Required Lenient name val) Request = ParamNotFound
+type instance Attribute (QueryParam Optional Strict name val) Request = Maybe val
+type instance Absence (QueryParam Optional Strict name val) = ParamParseError
 
-instance Trait (QueryParam Optional Lenient name val) Request where
-  type Attribute (QueryParam Optional Lenient name val) Request = Maybe (Either Text val)
+type instance Attribute (QueryParam Required Lenient name val) Request = Either Text val
+type instance Absence (QueryParam Required Lenient name val) = ParamNotFound
 
-instance TraitAbsence (QueryParam Optional Lenient name val) Request where
-  type Absence (QueryParam Optional Lenient name val) Request = Void
+type instance Attribute (QueryParam Optional Lenient name val) Request = Maybe (Either Text val)
+type instance Absence (QueryParam Optional Lenient name val) = Void
 
-type instance Prerequisite (QueryParam e p name val) ts Request = ()
+type instance Prerequisite (QueryParam e p name val) ts = ()
 
 queryParamHandler ::
   forall name val e p h ts.
-  (Get h (QueryParam e p name val) Request, ArrowChoice h) =>
-  h (Request `With` ts, Absence (QueryParam e p name val) Request) Response ->
+  (Get h (QueryParam e p name val), ArrowChoice h) =>
+  h (Request `With` ts, Absence (QueryParam e p name val)) Response ->
   Middleware h ts (QueryParam e p name val : ts)
 queryParamHandler errorHandler nextHandler = proc request -> do
   result <- probe QueryParam -< request
@@ -116,7 +104,7 @@
 -}
 queryParam ::
   forall name val h ts.
-  (Get h (QueryParam Required Strict name val) Request, ArrowChoice h) =>
+  (Get h (QueryParam Required Strict name val), ArrowChoice h) =>
   h (Request `With` ts, Either ParamNotFound ParamParseError) Response ->
   Middleware h ts (QueryParam Required Strict name val : ts)
 queryParam = queryParamHandler
@@ -134,7 +122,7 @@
 -}
 optionalQueryParam ::
   forall name val h ts.
-  (Get h (QueryParam Optional Strict name val) Request, ArrowChoice h) =>
+  (Get h (QueryParam Optional Strict name val), ArrowChoice h) =>
   h (Request `With` ts, ParamParseError) Response ->
   Middleware h ts (QueryParam Optional Strict name val : ts)
 optionalQueryParam = queryParamHandler
@@ -152,7 +140,7 @@
 -}
 lenientQueryParam ::
   forall name val h ts.
-  (Get h (QueryParam Required Lenient name val) Request, ArrowChoice h) =>
+  (Get h (QueryParam Required Lenient name val), ArrowChoice h) =>
   h (Request `With` ts, ParamNotFound) Response ->
   Middleware h ts (QueryParam Required Lenient name val : ts)
 lenientQueryParam = queryParamHandler
@@ -170,7 +158,7 @@
 -}
 optionalLenientQueryParam ::
   forall name val h ts.
-  (Get h (QueryParam Optional Lenient name val) Request, ArrowChoice h) =>
+  (Get h (QueryParam Optional Lenient name val), ArrowChoice h) =>
   Middleware h ts (QueryParam Optional Lenient name val : ts)
 optionalLenientQueryParam = queryParamHandler $ arr (absurd . snd)
 {-# INLINE optionalLenientQueryParam #-}
diff --git a/src/WebGear/Core/Trait/Status.hs b/src/WebGear/Core/Trait/Status.hs
--- a/src/WebGear/Core/Trait/Status.hs
+++ b/src/WebGear/Core/Trait/Status.hs
@@ -54,247 +54,246 @@
 
 import qualified Network.HTTP.Types as HTTP
 import WebGear.Core.Response (Response (..), ResponseBody (ResponseBodyBuilder))
-import WebGear.Core.Trait (Set, Trait (..), With, plant, wzero)
+import WebGear.Core.Trait (Attribute, Set, With, plant, wzero)
 
 -- | HTTP response status
 newtype Status = Status HTTP.Status
 
-instance Trait Status Response where
-  type Attribute Status Response = HTTP.Status
+type instance Attribute Status Response = HTTP.Status
 
 -- | Generate a response with the specified status
-mkResponse :: (Set h Status Response) => HTTP.Status -> h () (Response `With` '[Status])
+mkResponse :: (Set h Status) => HTTP.Status -> h () (Response `With` '[Status])
 mkResponse status = proc () -> do
   let response = wzero $ Response status [] (ResponseBodyBuilder mempty)
   plant (Status status) -< (response, status)
 {-# INLINE mkResponse #-}
 
 -- | Continue 100 response
-continue100 :: (Set h Status Response) => h () (Response `With` '[Status])
+continue100 :: (Set h Status) => h () (Response `With` '[Status])
 continue100 = mkResponse HTTP.continue100
 {-# INLINE continue100 #-}
 
 -- | Switching Protocols 101 response
-switchingProtocols101 :: (Set h Status Response) => h () (Response `With` '[Status])
+switchingProtocols101 :: (Set h Status) => h () (Response `With` '[Status])
 switchingProtocols101 = mkResponse HTTP.switchingProtocols101
 {-# INLINE switchingProtocols101 #-}
 
 -- | OK 200 response
-ok200 :: (Set h Status Response) => h () (Response `With` '[Status])
+ok200 :: (Set h Status) => h () (Response `With` '[Status])
 ok200 = mkResponse HTTP.ok200
 {-# INLINE ok200 #-}
 
 -- | Created 201 response
-created201 :: (Set h Status Response) => h () (Response `With` '[Status])
+created201 :: (Set h Status) => h () (Response `With` '[Status])
 created201 = mkResponse HTTP.created201
 {-# INLINE created201 #-}
 
 -- | Accepted 202 response
-accepted202 :: (Set h Status Response) => h () (Response `With` '[Status])
+accepted202 :: (Set h Status) => h () (Response `With` '[Status])
 accepted202 = mkResponse HTTP.accepted202
 {-# INLINE accepted202 #-}
 
 -- | Non-Authoritative 203 response
-nonAuthoritative203 :: (Set h Status Response) => h () (Response `With` '[Status])
+nonAuthoritative203 :: (Set h Status) => h () (Response `With` '[Status])
 nonAuthoritative203 = mkResponse HTTP.nonAuthoritative203
 {-# INLINE nonAuthoritative203 #-}
 
 -- | No Content 204 response
-noContent204 :: (Set h Status Response) => h () (Response `With` '[Status])
+noContent204 :: (Set h Status) => h () (Response `With` '[Status])
 noContent204 = mkResponse HTTP.noContent204
 {-# INLINE noContent204 #-}
 
 -- | Reset Content 205 response
-resetContent205 :: (Set h Status Response) => h () (Response `With` '[Status])
+resetContent205 :: (Set h Status) => h () (Response `With` '[Status])
 resetContent205 = mkResponse HTTP.resetContent205
 {-# INLINE resetContent205 #-}
 
 -- | Partial Content 206 response
-partialContent206 :: (Set h Status Response) => h () (Response `With` '[Status])
+partialContent206 :: (Set h Status) => h () (Response `With` '[Status])
 partialContent206 = mkResponse HTTP.partialContent206
 {-# INLINE partialContent206 #-}
 
 -- | Multiple Choices 300 response
-multipleChoices300 :: (Set h Status Response) => h () (Response `With` '[Status])
+multipleChoices300 :: (Set h Status) => h () (Response `With` '[Status])
 multipleChoices300 = mkResponse HTTP.multipleChoices300
 {-# INLINE multipleChoices300 #-}
 
 -- | Moved Permanently 301 response
-movedPermanently301 :: (Set h Status Response) => h () (Response `With` '[Status])
+movedPermanently301 :: (Set h Status) => h () (Response `With` '[Status])
 movedPermanently301 = mkResponse HTTP.movedPermanently301
 {-# INLINE movedPermanently301 #-}
 
 -- | Found 302 response
-found302 :: (Set h Status Response) => h () (Response `With` '[Status])
+found302 :: (Set h Status) => h () (Response `With` '[Status])
 found302 = mkResponse HTTP.found302
 {-# INLINE found302 #-}
 
 -- | See Other 303 response
-seeOther303 :: (Set h Status Response) => h () (Response `With` '[Status])
+seeOther303 :: (Set h Status) => h () (Response `With` '[Status])
 seeOther303 = mkResponse HTTP.seeOther303
 {-# INLINE seeOther303 #-}
 
 -- | Not Modified 304 response
-notModified304 :: (Set h Status Response) => h () (Response `With` '[Status])
+notModified304 :: (Set h Status) => h () (Response `With` '[Status])
 notModified304 = mkResponse HTTP.notModified304
 {-# INLINE notModified304 #-}
 
 -- | Temporary Redirect 307 response
-temporaryRedirect307 :: (Set h Status Response) => h () (Response `With` '[Status])
+temporaryRedirect307 :: (Set h Status) => h () (Response `With` '[Status])
 temporaryRedirect307 = mkResponse HTTP.temporaryRedirect307
 {-# INLINE temporaryRedirect307 #-}
 
 -- | Permanent Redirect 308 response
-permanentRedirect308 :: (Set h Status Response) => h () (Response `With` '[Status])
+permanentRedirect308 :: (Set h Status) => h () (Response `With` '[Status])
 permanentRedirect308 = mkResponse HTTP.permanentRedirect308
 {-# INLINE permanentRedirect308 #-}
 
 -- | Bad Request 400 response
-badRequest400 :: (Set h Status Response) => h () (Response `With` '[Status])
+badRequest400 :: (Set h Status) => h () (Response `With` '[Status])
 badRequest400 = mkResponse HTTP.badRequest400
 {-# INLINE badRequest400 #-}
 
 -- | Unauthorized 401 response
-unauthorized401 :: (Set h Status Response) => h () (Response `With` '[Status])
+unauthorized401 :: (Set h Status) => h () (Response `With` '[Status])
 unauthorized401 = mkResponse HTTP.unauthorized401
 {-# INLINE unauthorized401 #-}
 
 -- | Payment Required 402 response
-paymentRequired402 :: (Set h Status Response) => h () (Response `With` '[Status])
+paymentRequired402 :: (Set h Status) => h () (Response `With` '[Status])
 paymentRequired402 = mkResponse HTTP.paymentRequired402
 {-# INLINE paymentRequired402 #-}
 
 -- | Forbidden 403 response
-forbidden403 :: (Set h Status Response) => h () (Response `With` '[Status])
+forbidden403 :: (Set h Status) => h () (Response `With` '[Status])
 forbidden403 = mkResponse HTTP.forbidden403
 {-# INLINE forbidden403 #-}
 
 -- | Not Found 404 response
-notFound404 :: (Set h Status Response) => h () (Response `With` '[Status])
+notFound404 :: (Set h Status) => h () (Response `With` '[Status])
 notFound404 = mkResponse HTTP.notFound404
 {-# INLINE notFound404 #-}
 
 -- | Method Not Allowed 405 response
-methodNotAllowed405 :: (Set h Status Response) => h () (Response `With` '[Status])
+methodNotAllowed405 :: (Set h Status) => h () (Response `With` '[Status])
 methodNotAllowed405 = mkResponse HTTP.methodNotAllowed405
 {-# INLINE methodNotAllowed405 #-}
 
 -- | Not Acceptable 406 response
-notAcceptable406 :: (Set h Status Response) => h () (Response `With` '[Status])
+notAcceptable406 :: (Set h Status) => h () (Response `With` '[Status])
 notAcceptable406 = mkResponse HTTP.notAcceptable406
 {-# INLINE notAcceptable406 #-}
 
 -- | Proxy Authentication Required 407 response
-proxyAuthenticationRequired407 :: (Set h Status Response) => h () (Response `With` '[Status])
+proxyAuthenticationRequired407 :: (Set h Status) => h () (Response `With` '[Status])
 proxyAuthenticationRequired407 = mkResponse HTTP.proxyAuthenticationRequired407
 {-# INLINE proxyAuthenticationRequired407 #-}
 
 -- | Request Timeout 408 response
-requestTimeout408 :: (Set h Status Response) => h () (Response `With` '[Status])
+requestTimeout408 :: (Set h Status) => h () (Response `With` '[Status])
 requestTimeout408 = mkResponse HTTP.requestTimeout408
 {-# INLINE requestTimeout408 #-}
 
 -- | Conflict 409 response
-conflict409 :: (Set h Status Response) => h () (Response `With` '[Status])
+conflict409 :: (Set h Status) => h () (Response `With` '[Status])
 conflict409 = mkResponse HTTP.conflict409
 {-# INLINE conflict409 #-}
 
 -- | Gone 410 response
-gone410 :: (Set h Status Response) => h () (Response `With` '[Status])
+gone410 :: (Set h Status) => h () (Response `With` '[Status])
 gone410 = mkResponse HTTP.gone410
 {-# INLINE gone410 #-}
 
 -- | Length Required 411 response
-lengthRequired411 :: (Set h Status Response) => h () (Response `With` '[Status])
+lengthRequired411 :: (Set h Status) => h () (Response `With` '[Status])
 lengthRequired411 = mkResponse HTTP.lengthRequired411
 {-# INLINE lengthRequired411 #-}
 
 -- | Precondition Failed 412 response
-preconditionFailed412 :: (Set h Status Response) => h () (Response `With` '[Status])
+preconditionFailed412 :: (Set h Status) => h () (Response `With` '[Status])
 preconditionFailed412 = mkResponse HTTP.preconditionFailed412
 {-# INLINE preconditionFailed412 #-}
 
 -- | Request Entity Too Large 413 response
-requestEntityTooLarge413 :: (Set h Status Response) => h () (Response `With` '[Status])
+requestEntityTooLarge413 :: (Set h Status) => h () (Response `With` '[Status])
 requestEntityTooLarge413 = mkResponse HTTP.requestEntityTooLarge413
 {-# INLINE requestEntityTooLarge413 #-}
 
 -- | Request URI Too Long 414 response
-requestURITooLong414 :: (Set h Status Response) => h () (Response `With` '[Status])
+requestURITooLong414 :: (Set h Status) => h () (Response `With` '[Status])
 requestURITooLong414 = mkResponse HTTP.requestURITooLong414
 {-# INLINE requestURITooLong414 #-}
 
 -- | Unsupported Media Type 415 response
-unsupportedMediaType415 :: (Set h Status Response) => h () (Response `With` '[Status])
+unsupportedMediaType415 :: (Set h Status) => h () (Response `With` '[Status])
 unsupportedMediaType415 = mkResponse HTTP.unsupportedMediaType415
 {-# INLINE unsupportedMediaType415 #-}
 
 -- | Requested Range Not Satisfiable 416 response
-requestedRangeNotSatisfiable416 :: (Set h Status Response) => h () (Response `With` '[Status])
+requestedRangeNotSatisfiable416 :: (Set h Status) => h () (Response `With` '[Status])
 requestedRangeNotSatisfiable416 = mkResponse HTTP.requestedRangeNotSatisfiable416
 {-# INLINE requestedRangeNotSatisfiable416 #-}
 
 -- | Expectation Failed 417 response
-expectationFailed417 :: (Set h Status Response) => h () (Response `With` '[Status])
+expectationFailed417 :: (Set h Status) => h () (Response `With` '[Status])
 expectationFailed417 = mkResponse HTTP.expectationFailed417
 {-# INLINE expectationFailed417 #-}
 
 -- | I'm A Teapot 418 response
-imATeapot418 :: (Set h Status Response) => h () (Response `With` '[Status])
+imATeapot418 :: (Set h Status) => h () (Response `With` '[Status])
 imATeapot418 = mkResponse HTTP.imATeapot418
 {-# INLINE imATeapot418 #-}
 
 -- | Unprocessable Entity 422 response
-unprocessableEntity422 :: (Set h Status Response) => h () (Response `With` '[Status])
+unprocessableEntity422 :: (Set h Status) => h () (Response `With` '[Status])
 unprocessableEntity422 = mkResponse HTTP.unprocessableEntity422
 {-# INLINE unprocessableEntity422 #-}
 
 -- | Precondition Required 428 response
-preconditionRequired428 :: (Set h Status Response) => h () (Response `With` '[Status])
+preconditionRequired428 :: (Set h Status) => h () (Response `With` '[Status])
 preconditionRequired428 = mkResponse HTTP.preconditionRequired428
 {-# INLINE preconditionRequired428 #-}
 
 -- | Too Many Requests 429 response
-tooManyRequests429 :: (Set h Status Response) => h () (Response `With` '[Status])
+tooManyRequests429 :: (Set h Status) => h () (Response `With` '[Status])
 tooManyRequests429 = mkResponse HTTP.tooManyRequests429
 {-# INLINE tooManyRequests429 #-}
 
 -- | Request Header Fields Too Large 431 response
-requestHeaderFieldsTooLarge431 :: (Set h Status Response) => h () (Response `With` '[Status])
+requestHeaderFieldsTooLarge431 :: (Set h Status) => h () (Response `With` '[Status])
 requestHeaderFieldsTooLarge431 = mkResponse HTTP.requestHeaderFieldsTooLarge431
 {-# INLINE requestHeaderFieldsTooLarge431 #-}
 
 -- | Internal Server Error 500 response
-internalServerError500 :: (Set h Status Response) => h () (Response `With` '[Status])
+internalServerError500 :: (Set h Status) => h () (Response `With` '[Status])
 internalServerError500 = mkResponse HTTP.internalServerError500
 {-# INLINE internalServerError500 #-}
 
 -- | Not Implemented 501 response
-notImplemented501 :: (Set h Status Response) => h () (Response `With` '[Status])
+notImplemented501 :: (Set h Status) => h () (Response `With` '[Status])
 notImplemented501 = mkResponse HTTP.notImplemented501
 {-# INLINE notImplemented501 #-}
 
 -- | Bad Gateway 502 response
-badGateway502 :: (Set h Status Response) => h () (Response `With` '[Status])
+badGateway502 :: (Set h Status) => h () (Response `With` '[Status])
 badGateway502 = mkResponse HTTP.badGateway502
 {-# INLINE badGateway502 #-}
 
 -- | Service Unavailable 503 response
-serviceUnavailable503 :: (Set h Status Response) => h () (Response `With` '[Status])
+serviceUnavailable503 :: (Set h Status) => h () (Response `With` '[Status])
 serviceUnavailable503 = mkResponse HTTP.serviceUnavailable503
 {-# INLINE serviceUnavailable503 #-}
 
 -- | Gateway Timeout 504 response
-gatewayTimeout504 :: (Set h Status Response) => h () (Response `With` '[Status])
+gatewayTimeout504 :: (Set h Status) => h () (Response `With` '[Status])
 gatewayTimeout504 = mkResponse HTTP.gatewayTimeout504
 {-# INLINE gatewayTimeout504 #-}
 
 -- | HTTP Version Not Supported 505 response
-httpVersionNotSupported505 :: (Set h Status Response) => h () (Response `With` '[Status])
+httpVersionNotSupported505 :: (Set h Status) => h () (Response `With` '[Status])
 httpVersionNotSupported505 = mkResponse HTTP.httpVersionNotSupported505
 {-# INLINE httpVersionNotSupported505 #-}
 
 -- | Network Authentication Required 511 response
-networkAuthenticationRequired511 :: (Set h Status Response) => h () (Response `With` '[Status])
+networkAuthenticationRequired511 :: (Set h Status) => h () (Response `With` '[Status])
 networkAuthenticationRequired511 = mkResponse HTTP.networkAuthenticationRequired511
 {-# INLINE networkAuthenticationRequired511 #-}
diff --git a/src/WebGear/Core/Traits.hs b/src/WebGear/Core/Traits.hs
--- a/src/WebGear/Core/Traits.hs
+++ b/src/WebGear/Core/Traits.hs
@@ -17,8 +17,6 @@
 import qualified Data.Text.Lazy as LText
 import WebGear.Core.Handler (Handler)
 import WebGear.Core.MIMETypes (PlainText)
-import WebGear.Core.Request (Request)
-import WebGear.Core.Response (Response)
 import WebGear.Core.Trait (Gets, Sets)
 import WebGear.Core.Trait.Auth.Basic
 import WebGear.Core.Trait.Auth.Common
@@ -40,13 +38,13 @@
 -}
 type StdHandler h m =
   ( Handler h m
-  , Gets h [Method, Path, PathEnd] Request
+  , Gets h [Method, Path, PathEnd]
   , Sets
       h
       '[ Status
        , Body PlainText String
        , Body PlainText Text.Text
        , Body PlainText LText.Text
+       , RequiredResponseHeader "Content-Type" Text.Text
        ]
-      Response
   )
diff --git a/webgear-core.cabal b/webgear-core.cabal
--- a/webgear-core.cabal
+++ b/webgear-core.cabal
@@ -1,7 +1,7 @@
 cabal-version:       2.4
 
 name:                webgear-core
-version:             1.2.0
+version:             1.3.0
 synopsis:            Composable, type-safe library to build HTTP APIs
 description:
         WebGear is a library to for building composable, type-safe HTTP APIs.