What documentation is there on the extras will be provided with Android intents?
Update:
I did some further investigation. I understand that we can are meant to assume each intent to parses no data or extras unless explicitly documented. Additionally, some, but not all, extras mention which they are applicable to (see the android documentation and search for Standard Extra Data). We are expected to then look at what the intent does (or guess from its name) to understand more clearly what the extra does. Those which don't mention this are expected to be used in a large range of applications.