a public API is coming! no promises on timelines yet but it's important to us to get it shipped.
It'd be nice to support a "standard" API like MetaWeblog if at all possible. I know some of those (including that one!) is old and creaky, but it's old and creaky—and already has existing tools that work with it. A more modern incarnation of that might be Micropub.
(Also, I noted the "documentation is hard" in Jae's link. If you need help with that, you might able to ping me, depending on time constraints [yours and mine] -- I'm actually a technical writer who specializes in documenting developer APIs!)
Since you're working on an API, I might I suggest the following:
* [IndieAuth](https://indieweb.org/IndieAuth) (itself an extension to OAuth) for login/authentication
* [Micropub](https://indieweb.org/Micropub) for submitting and editing posts
This combination would immediately make cohost work very well as part of the IndieWeb and could make use of the many existing micropub clients out there (so you don't need to write your own mobile client), and would also allow things like using a Cohost account to sign in to IndieAuth-enabled websites as well.
+1, would be nice to be able to make clients for mobile :)
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