Model-Driven Development (MDD) is considered an effective technique for Internet of Things (IoT) application development. Our observation is that existing model-based approaches for IoT solutions focus on the software and systems perspective and show a need for more integration with organizational and business model aspects. Therefore, we developed a method and tool support for developing IoT applications in the field of air conditioning facilities. In this work, we applied quality criteria to evaluate the included Domain-Specific Modeling Language (DSML). To practically validate the modeling language as such and also the way it can be used and supported by the tool, we performed a real-world use case. The main contributions of this paper are a quality evaluation of the DSML and the tool support and lessons learned from both.