In this paper we present the architecture of a conversation engine aimed to simulate an interview process between a human and a computer player. This component is a central element of many serious games where educational goal is to develop player communication skills. We demonstrate the use of our engine in AgileDoctor, a serious game project for training medical students and general practitioners to communicate with their patients, so as to improve their long-term relationship and provide a higher quality health care. Our proposed conversation engine uses a generic method to combine the game scenario and the educational objectives. The game scenario is described by an instance of a model that formalizes the general doctor-patient interview process and the skills to develop. The conversation engine is able to use this model to engage a challenging dialogue with a human player where missing skills are focused. The proposed design methodology is not bound to the health domain and is transferable to a large range of educational usages