How do I send and receive privatemsg? I'm using Services with Drupal 7 and I built a rest service with it, I also included the Privatemsg module and the Entity API module.

I can see under the my service a resource called entity_privatemsg_message it has only retrieve and index as operations.

I also found a pm_service supported in drupal threads by someusers here :
 Add Service methods .

Now I can see also the privatemsg resource in my service. but I'm missing the documentation on how to send and receive pm message over the rest service. what kind of arguments should be sent with the request.  I'm working with js/jquery to make request calls  ($.ajax).

Thanks for any help  about the private message services.
I'm pretty sure that using Services Entity API  will provide what you are looking for.  An endpoint shows up for me after enabling the module.

This module provides support for all Entity API entity types to Services. All entity types get a standard resource, similar to what Services provides for code entity types such as nodes.
This module allows to get entities by properties or fields and also paging and related entities that are defined properly.