Interactions between humans and smart products (i.e. digital components integrated in physical Internet of Things devices) are becoming more complex and less visible. Yet designers lack tools to capture these interactions and incorporate them into their design. In this paper we present the Human-Computer-Context Interaction (HCCI) tool that helps the designer to consider the different interactions of the user early in the conceptualisation phase, in order to eventually improve the user experience for smart products. This tool introduces 5 relevant interaction levels to be considered, when defining the context-of-use. In this paper we assess the use of the tool by means of a design challenge with a total of 34 industrial design students, given the task to design a smart kitchen concept. The tool was evaluated by a mixed method approach. Results show that the tool was evaluated as useful and usable during the early concept phase of the design of smart products. Unsupported concepts typically envisioned a single user interacting with one object through explicit interactions. Hence, tool-supported designs were more holistic and better captured interactions with other objects, users, content and services. From this we conclude that the tool can help to detect possible pitfalls of design selections. The tool is aimed to be used in a new product development process by HCI researchers, designers, and developers and is technology independent. Based on observations and participant feedback, we reflect on the strengths and limitations of this tool.