Is there a right or wrong way to play a game? Many think not. Some have argued that, when we insist that players obey the rules of a game, we give too much weight to the author’s intent. Others have argued that such obedience to the rules violates the true purpose of games, which is fostering free and creative play. Both of these responses, I argue, misunderstand the nature of games and their rules. The rules do not tell us how to interpret a game; they merely tell us what the game is. And the point of the rules is not always to foster free and creative play. The point can be, instead, to communicate a sculpted form of activity. And in games, as with any form of communication, we need some shared norms to ground communicative stability. Games have what has been called a “prescriptive ontology.” A game is something more than simply a piece of material. It is some material as approached in a certain specified way. These prescriptions help to fix a common object of attention. Games share this prescriptive ontology with more traditional kinds of works. Novels are more than just a set of words on a page; they are those words read in a certain order. Games are more than just some software or cardboard bits; they are those bits interacted with according to certain rules. Part of a game’s essential nature is the prescriptions for how we are to play it. What’s more, we investigate the prescriptive ontology of games, we will uncover at least distinct prescriptive categories of games. Party games prescribe that we encounter the game once; heavy strategy games prescribe we encounter the game many times; and community evolution games prescribe that we encounter the game while embedded in an ongoing community of play.