If you go to https://github.com/Baltoli/hubski-api-spec you can see the API spec as we develop it. Watching how we (user92 and I, so far) design it should be very informative for you. If you've got any questions about APIs in general, feel free to ask, and I'm more than happy to help you.
Looks good! Any particular reason you are using POST only? If I want to update a comment or something it would be nice if the API supported a PUT request rather than POST. PUT would be idempotent also so if the first request failed I could reissue the same request and not suffer any ill effect... Looks good so far, keep up the good work.
Awesome, watching already. I'm working on a Win 8 app currently, hopefully I'll be able to use what you guys are developing.