Standard Failure Response 📰

<?xml version="1.0" encoding="UTF-8"?>
<Error>
   <Message></Message>
   <Details></Details><!-- Further/lengthier details of the error (if there are any)-->
</Error>

JSON error response 

For the cases where the API is to return JSON (ie: the request has set the Accept header field value to application/json) then the error format is as follows:

{
    "Error": {
        "Message": /* ...The error message... */,
        "Details": /* ...Further/lengthier details of the error (if there are any).. */
     }
}