Abstract Formal veri cation toolkits are typically of rather special and, if one compares di erent related toolkits to each other, complementary functionalities. It has therefore been proposed to integrate di erent related toolkits within common environments. The potential for such integration is a direct consequence of the very fact that formal veri cation toolkits are semantics-based in the sense that they are implementations of well-understood mathematical theories. We argue that Web services can serve as a new platform for addressing the more practical issues in connection with that: For one, service integration in general is certainly an essential ingredient of the Web service paradigm. Also, Web services promote distributed and open integration, which ts the decentralisation and dynamism of formal veri cation community. Furthermore, directory-like techniques help to tackle coordination issues in formal methods tool integration.