The semantic web promises automated invocation, discovery, and composition of web services by enhancing services with semantic descriptions. One such language used for creating semantic descriptions is the Web Ontology Language or OWL. An upper ontology for web services called OWL-S has been created to provide a mechanism for describing service semantics in a standard, well-defined manner. Unfortunately, the learning curve for semantic-rich description languages such as OWL-S can be steep, especially with given the current state of tool support for the language. This paper describes an automated software tool that uses model-driven architecture (MDA) techniques to generate an OWL-S description of a web service from a UML model. This allows the developer to focus on creating a model of the web service in a standard UML tool, leveraging existing knowledge.