JSON API: Specification Status
JSON API is at a third release candidate state. This means that it is not yet stable, however, libraries intended to work with 1.0 should implement this version of the specification. We may make very small tweaks, but everything is basically in place.
Work on this specification is being done at its GitHub repository. Please feel free to help flesh it out or, if you try to write an implementation, to tell us where things were ambiguous. The best way to do so is to file an Issue.