With the latest changes to Jersey you can now get information on such dynamic resources by GETing the resource with an Accept: application/vnd.sun.wadl+xml header that specifies that you want WADL rather than another representation. The Jersey runtime will inspect the object returned by the subresource locator and dynamically generate a WADL description.
Now WADL finally gets interesting (see also this discussion).
Hm, is this really RESTful? I’ve always thought each representation should ‘represent’ the actual state/content of a resource and not a bunch of meta data. Isn’t a WADL file another resource, a sub-resource so to say?