Tiny Thief belongs to a very specific subset of the adventure genre, best illustrated by Amanita Design's Samorost browser games.
We can be even more precise than that, in fact. Tiny Thief, developed by Barcelona indie studio 5 Ants and published under the Rovio Stars umbrella, does have a little bit of stealth, but it's more point-and-click adventure than full-time sneak-'em-up. Whenever thievery is the focus of a game, it's natural to assume that the result will fall into the stealth genre.
