Jason is a platform for the development of multi-agent systems. An extension of the AgentSpeak agent-oriented programming language is used to program the behaviour of individual agents. Jason is developed in Java and allows the customisation of most aspects of an agent or a multi-agent system. It comes as a plugin for either jEdit or Eclipse, and different infra-structures for the deployment of a multi-agent system, for example using JADE or SACI as an agent-based distributed system middleware.