In case of errors, they may contain an Message field with a description of the error. The HTTP status code will also indicate the type of error.

HTTP Response Code	Error Description
200	Successful request
201	Successful creation of a resource
400	Sending invalid JSON
401	Using an invalid OAuth token
403	Using an OAuth token without sufficient permissions
404	Calling an endpoint which does not exist
409	Creating a resource which already exists
422	Sending invalid fields
423	Calling an endpoint which is not allowed
429	Hitting a rate limit
500	An internal server error
503	External service errors (as an example, Payment Providers)