Where is the documentation for writing an OS X accessibility client?

Question

Apple has documentation for adding accessibility information to one's own app. This allows accessibility clients to control that app. However, I can find no information writing one's own accessibility client. I'd like to control other apps through their UI from an OS X application (not via AppleScript, ScriptingBridge, or a third part framework, BTW). I'd like to write a real accessibility client--where is the documentation for doing this?

This is what I've found so far:

• Manually sending Quartz events. This is a much lower level than the new Accessibility tools that come with OS X Yosemite.
• An old Carbon framework. This doesn't work on 64-bit Macs. Pretty-much useless today.
• This header file has some information about controlling an application. It's just a header file--no guide, no examples. I also can't see how to get from this structure to the methods in the protocol described in 1.

Answer 1

The header files are pretty much it, there is an example called UI Element Inspector

Opening the actual header file in the SDK might be helpful as there are a lot of comments and documentation which might not be available on the website