Honestly, having just played around with it, it absolutely would have just magic'd up some exotic steeds if they'd requested it cold. I tried things like "look at Dave", Dave having never been mentioned before, and it happily described Dave.

It can probably be dissuaded from doing so by using a prompt that makes it clear that non sequiturs are not allowed and players cannot just conjure things out of thin air at will. Not without an appropriate spell, anyway.