In open MAS, agent interaction protocols need to be pre-agreed to provide a basis for coordination and cooperation. Only if all agents agree on the protocols can they exchange data or engage in negotiations. Protocols define the exact sequence of messages and the admissable message content.

The FIPA Interaction Protocols Specification provides a number of known and adaptable protocols for several negatioation approaches. This includes auctions and voting schemes as well as simple queries.

Secure interactions are important in many scenarios. It is often necessary to complement the definition of secure interactions with additional infrastructure that has to be part of the system architecture. In such cases, e.g., when a public-key infrastructure has to be established, the corresponding concepts have to be integrated. This can be done during Apply Architectural Style.