I'd never heard of OPTIONS before. Do you have any links, besides [1], to more resource on it? Is this a common tactic, or is there a more standard way to add "discover-ability" to REST apis?

I usually try to mimic this kind of functionality with something like this [2]. But it always seems kludgy.

[1] http://www.w3.org/Protocols/rfc2616/rfc2616-sec9.html

[2] http://gemdash.tumblr.com/post/2798389935/restful-api-design [Half-assed attempt at an blog post]