Standard HTTP status codes and protocols Each error response returns the standard HTTP code number with the exception schema. KeyBank utilized the standard HTTP messaging so nothing too fancy.CodeStatusDescription200OK; SuccessfulThe action was successful. No additional actions are needed.400Missing mandatory informationRequest is missing required information.401Unauthorized requestInvalid credentials for the request.403Forbidden request accessYou do not have permission to complete the request.404Resource not foundThe resource for the request cannot be found.405Invalid request methodThe wrong request method was used.415Invalid request typeThe wrong media type submitted with the request.429Request timeoutThere are too many requests to the API and a timeout goes into effect.500Unknown errorThere was an unknown error with the server.502Bad gatewayThe servers cannot talk to each other or there is a miscommunication.503Unavailable serviceThe service is temporarily down.504Unable to process requestRequest needs more time to be processed.