We introduce a new service discovery and matchmaking architecture, layered on top of Globus MDS3, that integrates mutual trust evaluations into the matchmaking process. Our architecture adopts a symmetric approach, and checks trust policies of both grid users and resources without requiring policy disclosures. Our approach eliminates run-time security failures arising from incompatible user/resource pairs, seamlessly integrates user-side authorization tools with the matchmaking process, and protects na?ve grid users by allowing a security principal to define policies that control the list of discoverable resources.