This paper describes a multi-agent system, GraniteNights, modelled on the Agentcities project "evening agent" scenario. GraniteNights allows a user to plan an evening's entertainment in the city of Aberdeen, Scotland. The application fuses agent and Web technology, being viewed as an agent-based Web service. In particular, Semantic Web standards are used to a great extent in delivering the service. The paper argues that, in fact, the Semantic Web standards are more important for this type of application than the agent standards. A key feature of the application is component re-use: GraniteNights attempts to reuse without modification existing ontologies wherever possible; it also is comprised of a number of generic and thus wholly-reusable agents, including a user profiling agent and a constraint-based scheduler. The system is open in the sense that most of the individual agents can be invoked directly by external agent platforms, without going through the Web interface.