Abstract. Based on the plethora of proposals and standards for logic- and rulebased reasoning for the Semantic Web (SW), a key factor for the success of SW agents is interoperability of reasoning tasks. This paper reports on the first steps towards a framework for interoperable reasoning among agents in the SW that deploys third-party trusted reasoning services. This way, agents can exchange their arguments, without the need to conform to a common rule or logic paradigm – via an external reasoning service, the receiving agent can grasp the semantics of the received rule set. The paper presents how a multi-agent system was extended with a third-party trusted defeasible reasoning service, which offers agents the ability of reasoning with incomplete and inconsistent information. In addition, a brokering trade scenario is presented that illustrates the usability of the approach.