This paper presents a novel approach for the engineering of capacity-driven Web services. By capacity, we mean how a Web service is empowered with several sets of operations from which it selectively triggers a set of operations with respect to some run-time environmental requirements. Because of the specificities of capacity-driven Web services compared to regular (i.e., mono-capacity) Web services, their engineering in terms of design, development, and deployment needs to be conducted in a complete specific way. Our approach define an engineering process composed of five steps: (1) to frame the requirements that could be put on these Web services, (2) to define capacities and how these capacities are triggered, and last but not least link these capacities to requirements, (3) to identify the processes in term of business logic that these Web services could implement, (4) to generate the source code, and (5) to generate the capacity-driven Web Services Description Language (c-WSDL).