The importance of methodologies for the construction of agent-based systems has recently begun to be recognised, and an increase in efforts directed at addressing this concern is currently being seen. Yet the focus of the majority of such work is on the design aspects of methodology or on the higher-level aspects of analysis. Of no less importance, however, are the behavioural requirements and specification of autonomous agents, which in some sense precede these phases of the development process. In this paper, we provide a detailed analysis of these requirements, and offer a preliminary view on how to focus design on meeting these requirements.