Designing electronic markets is a difficult task. Due to the complexities inherent to the design, the approach of market engineering provides a structured engineering process that divides the design process into phases and recommends methods to solve the tasks within the single design phases. This paper introduces the tool workbench CAME for designing electronic markets. The workbench supports all design phases of the market engineering process, starting from the conceptual design that configures the appropriate auction rules to the detail design and implementation, which automatically generates the platform running the specified auction rules.