This paper proposes a multi-agent system for the problems of resource discovery and management in Grid networks. The system performs the discovery and matching of requested Grid services with advertised ones, in order to find the most suitable services. The algorithm presented considers the availability of computing resources to be a critical factor for service discovery and matching, thereby ensuring load balancing in the overall Grid system. All vital tasks in the system are performed by stationary and mobile agents, cooperating together to automate the discovery and matching processes and to ultimately provide the user with the most relevant Grid service.