diff --git a/internal/domain/action.go b/internal/domain/action.go
index 5c75c23..de218ed 100644
--- a/internal/domain/action.go
+++ b/internal/domain/action.go
@@ -25,7 +25,7 @@ var (
 	ActionTicket = Action{uid: "ticket"}
 )
 
-var ErrActionUnknown error = NewError(ErrorCodeInvalidRequest, "unknown action method")
+var ErrActionUnknown error = NewError(ErrorCodeInvalidRequest, "unknown action method", "")
 
 // ParseAction parse string identifier of action into struct enum.
 func ParseAction(uid string) (Action, error) {
diff --git a/internal/domain/code_challenge_method.go b/internal/domain/code_challenge_method.go
index 9c6b371..023a7b7 100644
--- a/internal/domain/code_challenge_method.go
+++ b/internal/domain/code_challenge_method.go
@@ -54,7 +54,11 @@ var (
 	}
 )
 
-var ErrCodeChallengeMethodUnknown error = NewError(ErrorCodeInvalidRequest, "unknown code_challene_method")
+var ErrCodeChallengeMethodUnknown error = NewError(
+	ErrorCodeInvalidRequest,
+	"unknown code_challene_method",
+	"https://indieauth.net/source/#authorization-request",
+)
 
 //nolint: gochecknoglobals // NOTE(toby3d): maps cannot be constants
 var slugsMethods = map[string]CodeChallengeMethod{
diff --git a/internal/domain/email.go b/internal/domain/email.go
index 0abbae7..4c57861 100644
--- a/internal/domain/email.go
+++ b/internal/domain/email.go
@@ -11,7 +11,7 @@ type Email struct {
 	host string
 }
 
-var ErrEmailInvalid error = NewError(ErrorCodeInvalidRequest, "cannot parse email")
+var ErrEmailInvalid error = NewError(ErrorCodeInvalidRequest, "cannot parse email", "")
 
 // ParseEmail parse strings to email identifier.
 func ParseEmail(src string) (*Email, error) {
diff --git a/internal/domain/error.go b/internal/domain/error.go
index 0bfd70a..4981524 100644
--- a/internal/domain/error.go
+++ b/internal/domain/error.go
@@ -171,20 +171,25 @@ func (e Error) SetReirectURI(u *http.URI) {
 }
 
 // NewError creates a new Error with the stack pointing to the function call
-// line.
+// line number.
 //
 // If no code or ErrorCodeUndefined is provided, ErrorCodeAccessDenied will be
 // used instead.
-func NewError(code ErrorCode, description string) *Error {
+func NewError(code ErrorCode, description, uri string, requestState ...string) *Error {
 	if code == ErrorCodeUndefined {
 		code = ErrorCodeAccessDenied
 	}
 
+	var state string
+	if len(requestState) > 0 {
+		state = requestState[0]
+	}
+
 	return &Error{
 		Code:        code,
 		Description: description,
-		URI:         "",
-		State:       "",
+		URI:         uri,
+		State:       state,
 		frame:       xerrors.Caller(1),
 	}
 }
diff --git a/internal/domain/error_test.go b/internal/domain/error_test.go
index 42b9d22..9d4282b 100644
--- a/internal/domain/error_test.go
+++ b/internal/domain/error_test.go
@@ -7,6 +7,6 @@ import (
 )
 
 func ExampleNewError() {
-	fmt.Printf("%v", domain.NewError(domain.ErrorCodeInvalidRequest, "client_id MUST be provided"))
+	fmt.Printf("%v", domain.NewError(domain.ErrorCodeInvalidRequest, "client_id MUST be provided", ""))
 	// Output: invalid_request: client_id MUST be provided
 }
diff --git a/internal/domain/scope.go b/internal/domain/scope.go
index e11ebc7..7c36a76 100644
--- a/internal/domain/scope.go
+++ b/internal/domain/scope.go
@@ -20,7 +20,7 @@ type (
 	Scopes []Scope
 )
 
-var ErrScopeUnknown error = NewError(ErrorCodeInvalidRequest, "unknown scope")
+var ErrScopeUnknown error = NewError(ErrorCodeInvalidRequest, "unknown scope", "https://indieweb.org/scope")
 
 //nolint: gochecknoglobals // NOTE(toby3d): structs cannot be constants
 var (