From my list at http://techmikael.blogspot.no/2014/05/s15e03-query-variables-constant-trouble.html you can use the following variables in a REST query:
- Request (not useful as it return _vti_bin/client.svc)
Basically all which does not pull in a value from a specific context item.
Fill in your variables in the “Query Template” field of the SharePoint 2013 Query Tool and you get the syntax. Get the code and compile yourself and you will see the final expansion as well.