I've worked as contract help before.
If you've finished the process of interviewing, there's one of two possible outcomes. Either you got the job, or you didn't. If your recruiter is the one who arranged for these interviews, they'll want to discuss how it went and provide any feedback they've received.
The best thing I've found when working with ...
The most effective way I've found to get an opinion out if someone who is hesitant to give it is to ask them specific questions in a narrow scope. Consider the difference between
What did you think of the book?
I wasn't quite sure what to think of the character Maria. Sometimes she seems like a villain, but other times I felt bad for her. What do you ...
You be polite by agreeing to the call before you ask for the agenda. I'd also give the reason why you want to know, as being prepared for the call is good for both of you. So I'd reply with something like the following:
Sure, I'm available to talk at X time. So I can be prepared, what's the agenda for the call?
If "agenda" is too formal, then say ...