The less hoops you make someone jump through the better.
The agency has photographer X, whose rate they know; and photographer Y whose rate they don't know. All things being equal will they give the work to X (who is a known) or will they spend extra time contacting Y to find out her rates before deciding. People want an easy life so make it as easy as possible for them to pick you by including all the necessary information.
I am learning photo graphee - see the results at www.danmarchant.com