Describing content type usage

[pmackay]

I've read these docs and they are very useful. However the Content Types section seems a bit unclear, even after reading the Forms section as well. In Content Types you suggest it is best to use "application/x-resource+format" and "application/x-collection+format" as content types and have nothing more specific than that. The Forms section makes sense as far as a generic way to define form input, but how are clients to know what fields/properties they might get from a resource and what they can do with it? This is still a point of confusion in your approach for me.