We have the landing page on https://<vRPA_cluster_IP>/fapi/rest/5_2 and also the RESTAPI guide on support.emc.com. Feel free to email me if there are any specific questions.
Note that we'll be releasing RPVM 5.3 with a new modern RESTAPI which would co-exist with the current API. The new API would feature Swagger UI and also online documentation as part of developer.dellemc.com.
Hope that helps,
Idan Kentor Product Engineer - RecoverPoint and RecoverPoint for VMs @IdanKentor email@example.com