Contract design matters. The literature confirms that different contract designs can induce varying emotions, feelings, behaviour, and views of the contractual relationship. Specifically, prevention- and promotion-framed contracts and contract clauses seem to induce different emotions, which have been shown to impact the development of trust and even relationship performance. In addition, as many traditional contracts lack a design perspective, they may induce many negative emotions, such as confusion and frustration, among contract users. On the other hand, well-designed contracts can empower and engage contract users. Although (emotional) AI enables new venues for contract design and legal technology related research, it requires the adoption of new research methodologies. This chapter presents a novel methodology for legal research—design science methodology—that originates from computer science and serves a dual purpose: creating new scientific knowledge while developing and evaluating an information systems artefact. To illustrate how the methodology can be applied in practice, the chapter presents a research setting in which design science methodology can be used for developing and evaluating an AI-based contract design tool that is based on the guiding principles of proactive contract theory and that takes into account the social and psycho-cognitive effects of contracts.