Is it correct to respond with partial representation for low capabilities media-types?

Hi,

would it be correct for an application to provide partial resource
representation when providing a certain media-type?

My use case is that I have a user agent which don't have any
formatting capabilities nor metadata capabilities. Would it be correct
to "reserve" a specific media-type for that type of user agent so my
application can skip the generation of a bunch of markup and metadata
as a representation? And sometimes the reason is just that I don't
want to exhaust the user agent.

Are there any rules to follow when deciding to NOT include a specific
part of a representation for a specific media-type? Like: "If the
media-type can honor it you must include it"? Or judgment and best
effort is enough?

- Philippe