Most software engineering tools come with fixed functionality or limited plug-in extension capabilities. Building software development environments that support truly dynamic extension capabilities to incorporate a wide range of additional facilities at run-time has proved to be a very challenging task. We describe a new approach using web service components to support the dynamic discovery, integration and invocation of remote software tool facilities for JEdit, an open source Integrated Development Environment. In this approach discrete software tool functionality is encapsulated in software "toolets", accessed as remote web service-based components. These toolet services are registered and discovered, and then dynamically integrated and invoked from within the JEdit IDE as required. We describe the architecture of our approach, key design and implementation issues, and illustrate the feasibility of the approach with several prototype toolet components and results of their evaluation.