I fear I am the next nitwit of the day. I have just sent off material to an agent who requested it from my query. I queried her from information in Guide To Literary Agents. Now that there is a possibility that she might be interested I can find very little information on her. How do I get her author list? I'm afraid if I ask her for it I'll blow my chances of having her represent me if she is interested and is a good agent.
All agents are used to answering the question "who do you represent". It's absolutely standard, run of the mill. Any, and I mean this unilaterally, ANY agent who gets angry at you for asking should be avoided. If they act like you're a nitwit for asking, avoid them. If they act like you're bothering them, avoid them.
I'm not all that crazy about people calling me on the phone to ask, but if someone emails me, I have a form email that gives my client names and recent sales. I direct people to my website and to my Publishers Marketplace listing.
You do NOT qualify as nitwit of the day for asking these questions. You will qualify if you DON'T.
The best source of info is an agent's own website. If that is not forthcoming about clients, google the agent's name. If you don't get any hits other than listings, you should contact the agent directly. Politely of course. "Dear Agent with a Lousy Public Face: Can you direct me to information about who you represent and the projects you've recently sold. Thank you very much for your time, Sincerely Snarkling With Smarts".
If an agent is new to agenting, s/he will say so. Ask them about previous publishing experience.
If an agent can not or will not answer "who do you represent" and "what have you sold", avoid them.