There is no out of box documentation/test/support for Genie REST APIs through Knox. However Knox is architected in an extensible way and potentially can integrate with Genie or such REST APIs.
Knox allows a pluggable model for the pipeline of Authentication, Authorization, Audit, & other filters for every service that it is configured with. You will probably need to write some customer providers to do Genie specific things.
We can take this offline. You can reach me at firstname.lastname@example.org