Key Performance Indicators (KPIs) play an important role in guiding the management of business models throughout their lifecycle. However, existing research lacks practical methods to guide the definition of KPIs for business models. Without proper guidance, there may be a mismatch between the intended business model design and its implementation, resulting in many promising business model ideas failing to reach the market. To address this problem, we adopt a design science research approach to design and evaluate a method and supporting IT tool for defining business model KPIs. In this research-in-progress paper, we present a set of meta-requirements and design principles for developing the method and tool support. We instantiate the requirements and principles in a tool prototype and evaluate their validity in semi-structured interviews with five industry experts. Our study contributes to research on KPIs for business models and the development of methods and tools for business model management.