The usability of formal concepts for system design depends essentially on their integration in the design process. We discuss several possible levels of integration: technical integration of tools considering APIs and tool interfaces, conceptual integration of metamodels of description formalisms combined with hard and soft constraints, semantical integration of semantics of description techniques using a common semantic model, and finally methodical integration by an embedding in the development process. We show the feasibility of such an integrated approach and its advantages presenting AutoFocus/Quest, a formal method CASE-Tool with its levels of integration. Parts of a banking system model are used as example.