It is really your responsibility as a client if you have an agenda that you want to discuss. Another person might benefit from a T being more active or directing some of the conversation as you have described-- there is really no right or wrong way if it benefits the client-- but if you know what you need and want, therapy is a great place to begin to articulate that.

It has been my experience that it isn't so easy to *clearly* articulate what I want and sometimes I have to say a version of what skysblue suggested. Sometimes I don't realize that it veered from my agenda and it's been very interesting to go back in and say that X was on my agenda but I found the discussion really was about X.Y. but I didn't know how to say that at the time, or I only realized later. This kind of post hoc discussion of a discussion usually leads to something deeper, like how hard it is to be perfectly clear rather than kind of vaguish or how hard it is to realize I want something different right now but I don't know how to say that. Sometimes the discussions about something not on the agenda and why have moved the original topic forward in ways I didn't anticipate.