Rational agents' decisions are driven by their intentions, in the sense that agents execute actions that most probably lead to situations where their intentions are achieved. Using that insight, this paper proposes a method for 'intention checking': let a description of a game, a state and the action executed by the agent at that state be given, the method checks whether the agent acted with the intention to reach a situation where some proposition 'p' is true. We use a logic with epistemic and temporal operators to reason about games and extend it with an intention operator 'IX'. Formulas of the form 'IX(p)' are defined to be true in the situations where the intention check method verifies that the agent acts with the intention to achieve 'p' in the next state of the game. We show that this operator satisfies the principles of Bratman's Asymmetry Thesis, and we also compare it to other theories of intention.