Ah. We tend to give players a DC to beat (usually 10+HD), with success giving you the description blurb in the MM and the accurate answer to one question (typically: vulnerability, best/worst save, special ability). Extra questions for every 5 above the DC.

So a Wizard or Bard or equivalent typically knows that trolls are weak against fire and illithids eat your brains. A low skill/int character will struggle to recall anything useful.