Wireless Sensor Networks (WSNs) are still designed and deployed for one specific application, while it is vital to deploy several applications over the same WSN in order to reduce the deployment and the administrative costs. One of the remaining problems, in this domain, resides in the data aggregation solutions, which are proposed generally for one application and may drain the WSN power in a multi-application context. Therefore, we propose a data aggregation scheme based on a multi-agent system to aggregate the WSN information in an energy-efficient manner even if we are deploying several applications over this network. This proposal has proved its performance in the context of one and several applications through successive simulations in different network scales.