fae promises

Toot seemed to consider it, as though he might be inclined not to cooperate, then nodded. "Very well. You will have the information you wish. Release me."
I narrowed my eyes. "Are you sure? Do you promise?"
Toot stamped his foot again, scattering more silver dust motes. "Harry! You're ruining the drama!"
I folded my arms. "I want to hear you promise. "
Toot threw up his hands. "Fine, fine, fine! I promise, I promise, I promise! I'll dig up what you want to know!" He started to buzz about the circle in great agitation, wings lifting him easily into the air. "Let me out! Let me out!"
A promise thrice made is as close to absolute truth as you can get from a faery. I went quickly to the circle and scuffed over the line drawn in the dirt with my foot, willing the circle to part. It did, with a little hiss of released energy.
Toot streaked out over Lake Michigan's waters again, a miniature silver comet, and vanished in a twinkling, just like Santa Claus. Though I should say that Santa is a much bigger and more powerful faery than Toot, and I don't know his true name anyway. You'd never see me trying to nab Saint Nick in a magic circle, even if I did. I don't think anyone has stones that big.
I waited around, walking about to keep from falling asleep. If I did that, Toot would be perfectly within his rights as a faery to fulfill his promise by telling me the information while I was sleeping. And, given that I had just now captured and humiliated him, he'd probably do something to even the scales - two weeks from now he wouldn't even remember it, but if I let him have a free shot at me tonight, I might wake up with an ass's head, and I didn't think that would be good for business.

Storm Front Chapter 6, Page 66-67