I am adding Spine support for my engine(https://github.com/stubma/WiEngine), and also I am a backer of Spine. Spine is great and I like it.

I found the example json is not very completed, so is there a doc about the json format? Or, is there an example json which contains all keys?

hey luma, there is more documentation coming soon. Can't give you very much detail since Nate is the one doing all the code.
We'll get back to you

I'd like to have the JSON documented in the next day or so.