Abstract. We propose a declarative framework for modelling multi-agent systems and specify a number of properties of these systems and agents within them. The framework is parametric with respect to an input/output semantics for agents, whereby inputs are the agents’ observations, and outputs are their actions. The observations include actions performed by other agents and events happening in the world. We define the semantics of a multi-agent system via a stability condition over the individual agents’ semantics. We instantiate the framework with respect to simple abductive logic agents. We illustrate the framework and the proposed properties by means of a simple example of agent negotiation.