@MariaAbrahms:  Hmm... I wonder if we should remove the whole thing?  Maybe just:

    The &PRODNAME; API supports JSON data serialization formats only.
    The request body is assumed to be JSON, and the response body will
    be returned as JSON.

Does that sound ok?  And when we address the alternate content-type/accept headers, the docs can be updated to say that other header types will be rejected?