I've never seen value in self-describing or human readable messages. You need some kind of relatively unique identifier for the format of a given message and any optional payload, but beyond that, if a receiver doesn't have any code that knows what to do with a given message, what's the point of being able to deserialize it? And I think debugging an API without making tools is a waste of effort, for the same reason that you use curl rather than typing "POST..." into netcat.