Assistant teams extend the present view on personal assistance software. Instead of a single assistant, a team devotes an ensemble of agents to the private use of each user. It can provide a new variety of functionalities relying on the composition of individual services for the owner benefit. In this paper, we present a model of assistant teams based on the exploitation of extended agent interactions. In addition to the usual direct interactions among individuals, we introduce the concept of 'overhearing ' to let agent react to indirect events. We describe an architecture of such systems, address the concern of modeling their interaction infrastructures with a construction methodology, and detail an example scenario.