Web Services are the current most promising technology based on the concept of Service Oriented Computing that provides the basis for the development and execution of business processes that are distributed over the network and available via standard interfaces and protocols. Quality of Services (QoS) represents a major issue that covers the challenges in the service composition area and in the service oriented engineering. In this paper, we present the Web Services Design Tool (WSDTool). This tool allows the different actors involved in Web services design to define and address QoS requirements.