Yes you can in beautiful markdown language at https://<yourappurl>/rest-doc/ :)
It's currently only possible at the operation level (and resource level) in the configuration of your REST service.
Use markdown to format it correctly!
In my opinion it should be documented at the responses (instead of "succesful operation" ) but that is not currently possible.
Do you mean something like the information that you can find in the rest doc of your app: http://yourapp.com/rest-doc/