"Giving too much away"? That makes no sense, do you regularly sign up for stuff you have no idea what it's for?

You don't gain anything by hiding what your product is from potential users. If you're worried about someone stealing your idea, don't be (not that its a bad idea, it just doesn't generally happen like that).

I certainly wouldn't consider signing up with that little information.

Ask yourself how often you engage on a similar level if detail.