Applying coordination mechanisms to handle interdependencies that exist between agents in multi-agent systems (MASs), is an important issue. In this paper, two levels MAS modeling scheme and a language to describe a MAS plan based on interdependencies between agents' plans are proposed. Initially a generic study of possible interdependencies between agents in MASs is presented, followed by the formal modeling (using Colored Petri Nets) of coordination mechanisms for those dependencies. These mechanisms control the dependencies between agents to avoid unsafe interactions where individual agents' plans are merged into a global multi-agent plan. This separation, managed by the coordination mechanisms, offers more powerful modularity in MASs modeling.