Addressing urban health through the built environment requires cross-disciplinary approaches, where design plays a crucial role. Gaining insights from a design-led research perspective to find situated solutions for promoting healthy behaviours is a requirement that must be clarified. Therefore, we ask the following question: what kind of design research instruments may help in applying the urban health approach from a design-led perspective? With this research question, and to contribute to the mentioned issues to be clarified, this paper presents the application of a framework adopted in a local action research project, namely the Healthy Neighbourhoods Hub (HNH) research project. The HNH framework was used as a design research toolkit for collecting contextual data and identifying insights to build scenarios and strategies for all the involved design disciplines. Around 169 participants among local stakeholders and citizens in two case studies in the city of Florence (Italy) were involved in semi-structured interviews, Healthy Labs, and Open Space Lab. As a result, the participatory activities provided a wide variety of qualitative data, such as themes related to user needs (n = 15), critical issues and points of weakness (n = 32), potentialities and points of strength (n = 27), strategies (n = 38), design insights (n = 30), and a collection of 40 local projects (40 in 5 themes), that contributed to the subsequent co-design activities of the project. This richness suggests the potential of using the adopted resources to build the HNH Toolkit as a design research instrument for addressing urban health and gaining design knowledge for the promotion of healthy behaviours through the design of the built environment.