Hi @tom1, I enjoyed and starred your java projects on github! 
As nodejs developer, I’d like to implement (and I’ll glad to share on github) something similar to what you did in Java, splitting general/form actions cases.
To avoid to re-engineer your (well done) code (and the RASA core python code too), and avoiding to reinvent the wheel coding with trial & errors approach, my question to @akelad and any other RASA people:
There is any external Action server webhook HTTP API request/reply JSON payloads documentation/specification/details? If not I please ask to supply a clear API interface docs! 
BTW, I already read RASA docs, but info are insufficient immo, see issues raised:
Thanks
giorgio