If an error occurs when running RESTful web services, the web service will respond with a "400 Bad Request" HTTP status code.
The response will contain an "exception." In turn, this exception will contain an error code, a text with possible information about the error, and a (optional) "stack trace."
The exception will be sent either as a JSON structure or as an XML structure, depending on what the original request used.
The structure will contain the following values:
errorCode (integer) - Error number
errorMessage - Description of error
stackTrace - Stack trace on the server where the error occurred (usually only important for Support)