In open multi-agent systems (MASs) we cannot assume agents to be developed in a centralized fashion. Recent proposals of commitmentbased communication frameworks aim at increasing such openness. Interaction with agents whose behavior does not follow a universal standard raises the need for some means of protection for each agent. In this work we propose an automata-based monitoring module that continuously supports an agent during its life in a MAS. Such module includes a Word Composer that observes exchanged messages and keeps track of significant past interactions to express an agent's input in the form of time-stamped words, and a Word Analyzer that processes such words and matches them against some properties expressed in linear temporal logic which are supposed to hold throughout the interactions.