Abstract: Mainstreaming and industrializing agent technologies requires suitable methodological and technological support for the various engineering activities associated with managing the complexity of any software system development. Despite its origins in object oriented software engineering the UML provides a rich and extensible set of modeling constructs that can be applied to agent oriented technologies. This paper provides details of extensions to the UML for the design of agents that are to be implemented in the Jack language. These extensions provide the capacity to model the behavior of agents for purposes of design and, though the extensions are language specific, future generalisation and application to other agent languages can be supported as a industry-wide consensus about the nature of agency emerges over the next few years. This research builds on previously proposed extensions to the UML and moves a step closer to the goal of providing through-life engineering support to agent oriented systems development. This work is motivated by a pressing need to maintain, modify, develop and deploy existing and future agent based simulations of military operations for the Australian Defence Force.