We use standard HTTP codes in return to indicate both the success of a request and to indicate failure. Below are the codes used in our APIs:

CodeStatusDescription
200OkSuccess
201CreatedThe request is complete, and a new resource was created
400Bad RequestInvalid request due a validation error
401UnauthorizedAuthentication failure
403ForbiddenYour application is not authorized to access this environment
500Internal Server ErrorAn internal error has occurred