I had an interview and the agent wanted to know everything they're asked me and she was clearly making a note, but I was a little vague deliberately. When talking about a different role later she said she'd be able to prep me for the interview as she has someone else who's already been for interview for the role. I have come across this before but it strikes me as unfair in a way as I went into that interview unprepared as I was her first candidate and whoever goes in next has an advantage. Is it reasonable to say I'd rather not give you details as I want the role and I don't want you telling all this to your other candidate who is going in tomorrow?