Multi agent systems (MAS) are usually complicated and therefore error-prone. Especially the fact that there is a lot of interaction between agents can cause serious errors. In this paper we present an agent algebra which allows the formal description of MAS but also the verification of properties (safety and progress properties) of MAS. This can help the designer to become clear about the design and the correctness of the implementation. Our agent algebra can thus aid in making MAS suitable for control of safety critical systems such as flight control. Our agent algebra, whose terms, structured operational semantics and laws are described in this paper, focuses on interaction of agents. Thus, our agent algebra is especially suited for the description of cooperation and conflict (which is a major concern in MAS) among agents.