[randomdrake]

Agreed. I came here to post something similar but I was going to mention working with SOAP[1] in addition to what you mentioned. It sounds like the OP is trying to do something which sounded very much like using SOAP and XML to me.

To paraphrase the OP, "Since so many APIs can be described in similar terms, why don't we have some sort of standard that one can look at to identify how to use the API instead of letting the API speak for itself?"

When you start going down this track, you're not only making things complicated on the client's end of things. On the server side, you're having to maintain two things for the API now. First: the ruleset, ensuring it's 100% to spec lest a client fail. Second: the code generating the response in the first place.

I've built clients and servers for both RESTful and SOAPy APIs and I can say I would take REST any day.

[1] - http://en.wikipedia.org/wiki/SOAP