Attribute takes a URL as the argument. The URL points to a RCML document that will be executed while the caller (Agent) is put in the queue waiting for the next caller (Customer) to join . The waitUrl RCML only supports the Say, Play, and Redirect verbs. Once the waitUrl RCML flow runs out of verbs to execute, the Call Queue will start over, essentially looping hold music indefinitely. verb can be used for calling RCML document again and the Application can add some dynamic business logic that can change in the next loop.
The Call Queue will pass the parameters explained in Request Parameters in its request to the value of the waitUrl attribute.