In this paper is we apply insights from mechanism design to the design of agent interaction protocols. We show how this allows us a more flexible approach to the design of agent interaction protocols. By way of an analysis of a dialogue game from the literature we show how a protocol with many constraints on the moves allowed can be replaced by one in which we relax the rules, but make stronger assumptions on the type of participant that is involved in the dialogue. We can then use techniques from game theory and mechanism design to show that many of the constraints in the original protocol can be derived as properties of rational behavior.