Thrift has a compiler that generates pretty HTML documentation for a .thrift file. An example can be seen on the Evernote page (http://www.evernote.com/about/developer/api/ref/). I think it'd be valuable to offer the same for HBase and publish it on the website alongside the normal documentation. I've never worked with Forrest before but I'll have a look if I can find the correct place to insert this.
There is one ticket on Thrift that I'd like to see resolved first (