Web services are described and located using the Web Service Description Language (WSDL). While considerable tool support is available for generating WSDL descriptions from existing service interfaces, these tools may differ in how the generation is done. During the evolution of the service, its interface may also change, requiring the generation of a new WSDL description as well. Consequently, it is important to understand the WSDL descriptions and to be able to compare them e.g. for detecting changes due to the evolution of the service or the standards. In this paper we present an approach to analyze and compare WSDL descriptions at UML level. The approach has been applied to compare tool support available for constructing Web services in terms of WSDL descriptions they generate for the same example Web service. We have also explored and compared two different versions of a particular Web service and its interface using the proposed approach.