diff --git a/docs/standalone-signaling-api-v1.md b/docs/standalone-signaling-api-v1.md
index 1487d35..899f1fa 100644
--- a/docs/standalone-signaling-api-v1.md
+++ b/docs/standalone-signaling-api-v1.md
@@ -285,13 +285,18 @@ authorized, the backend returns an error and the hello request will be rejected.
 
 ### Error codes
 
-- `unsupported-version`: The requested version is not supported.
-- `auth-failed`: The session could not be authenticated.
-- `too-many-sessions`: Too many sessions exist for this user id.
+- `invalid_request`: The backend request for the v1 hello could not be authenticated. Check your shared secret.
+- `invalid_hello_version`: The requested `hello` version is not supported.
+- `auth_failed`: The session could not be authenticated.
 - `invalid_backend`: The requested backend URL is not supported.
 - `invalid_client_type`: The [client type](#client-types) is not supported.
+- `invalid_ticket`: The passed ticket in the v1 hello is invalid.
+- `no_such_user`: The user id in the v1 hello does not exists.
 - `invalid_token`: The passed token is invalid (can happen for
-  [client type `internal`](#client-type-internal)).
+  [client type `internal`](#client-type-internal) or v2 requests).
+- `token_not_valid_yet`: The token could be authenticated but is not valid yet.
+- `token_expired`: The token could be authenticated but is expired.
+- `too_many_requests`: Too many failed requests from this client.
 
 
 ### Client types
@@ -389,6 +394,7 @@ server will return an error and a normal `hello` handshake has to be performed.
 ### Error codes
 
 - `no_such_session`: The session id is no longer valid.
+- `too_many_requests`: Too many failed requests from this client.
 
 
 ## Releasing sessions
@@ -521,8 +527,11 @@ user, the backend returns an error and the room request will be rejected.
 
 ### Error codes
 
+- `invalid_request`: The backend request could not be authenticated. Check your shared secret.
 - `no_such_room`: The requested room does not exist or the user is not invited
   to the room.
+- `duplicate_session`: The given session already joined the room.
+- `room_join_failed`: The Talk backend returned an unexpected response while joining the room.
 
 
 ## Join federated room
diff --git a/hub.go b/hub.go
index 27d2bfd..89b147c 100644
--- a/hub.go
+++ b/hub.go
@@ -54,18 +54,31 @@ import (
 )
 
 var (
-	DuplicateClient     = NewError("duplicate_client", "Client already registered.")
-	HelloExpected       = NewError("hello_expected", "Expected Hello request.")
+	// HelloExpected is returned if a client sends a message before the "hello" request.
+	HelloExpected = NewError("hello_expected", "Expected Hello request.")
+	// InvalidHelloVersion is returned if the version in the "hello" message is not supported.
 	InvalidHelloVersion = NewError("invalid_hello_version", "The hello version is not supported.")
-	UserAuthFailed      = NewError("auth_failed", "The user could not be authenticated.")
-	RoomJoinFailed      = NewError("room_join_failed", "Could not join the room.")
-	InvalidClientType   = NewError("invalid_client_type", "The client type is not supported.")
-	InvalidBackendUrl   = NewError("invalid_backend", "The backend URL is not supported.")
-	InvalidToken        = NewError("invalid_token", "The passed token is invalid.")
-	NoSuchSession       = NewError("no_such_session", "The session to resume does not exist.")
-	TokenNotValidYet    = NewError("token_not_valid_yet", "The token is not valid yet.")
-	TokenExpired        = NewError("token_expired", "The token is expired.")
-	TooManyRequests     = NewError("too_many_requests", "Too many requests.")
+	// UserAuthFailed is returned if the Talk response to a v1 hello is not an error but also not a valid auth response.
+	UserAuthFailed = NewError("auth_failed", "The user could not be authenticated.")
+	// RoomJoinFailed is returned if the Talk response to a room join request is not an error and not a valid join response.
+	RoomJoinFailed = NewError("room_join_failed", "Could not join the room.")
+	// InvalidClientType is returned if the client type in the "hello" request is not supported.
+	InvalidClientType = NewError("invalid_client_type", "The client type is not supported.")
+	// InvalidBackendUrl is returned if no backend is configured for URL in the "hello" request.
+	InvalidBackendUrl = NewError("invalid_backend", "The backend URL is not supported.")
+	// InvalidToken is returned if the token in a "hello" request could not be validated.
+	InvalidToken = NewError("invalid_token", "The passed token is invalid.")
+	// NoSuchSession is returned if the session to be resumed is unknown or expired.
+	NoSuchSession = NewError("no_such_session", "The session to resume does not exist.")
+	// TokenNotValidYet is returned if the token in a "hello" request could be authenticated but is not valid yet.
+	// This hints to a mismatch in the time between the server running Talk and the server running the signaling server.
+	TokenNotValidYet = NewError("token_not_valid_yet", "The token is not valid yet.")
+	// TokenExpired is returned if the token in a "hello" request could be authenticated but is expired.
+	// This hints to a mismatch in the time between the server running Talk and the server running the signaling server,
+	// but could also be a client trying to connect with an old token.
+	TokenExpired = NewError("token_expired", "The token is expired.")
+	// TooManyRequests is returned if brute force detection reports too many failed "hello" requests.
+	TooManyRequests = NewError("too_many_requests", "Too many requests.")
 
 	// Maximum number of concurrent requests to a backend.
 	defaultMaxConcurrentRequestsPerHost = 8