Abstract: We propose a formal framework based on finite state processalgebra for modeling service coordination in agent systems. The model is inspired by WS-coordination specification. Several participant agents can coordinate their actions towards reaching a semantically consistent outcome in a distributed activity. The model defines coordinator and participant agents and their generic interaction protocols and allows integration of application specific protocols by means of protocol handlers. The approach is demonstrated by a sample model showing how coordination is achieved between a set of agents involved in contracting activities.