Urban green spaces contribute to the physical, mental, social, and environmental health of populations. To support local authorities in designing and managing health-promoting green spaces, the MyGreenSpace project is developing a tool to characterize the health potential of green spaces based on four functions identified in the scientific literature: mitigating exposure to environmental risk factors, developing individual capacities, providing opportunities for restoration, and supporting biodiversity. The tool relies primarily on OpenStreetMap (OSM) open data and collaboratively collected field data. A web platform enables the calculation of thirty-one indicators, the mapping of the health potential of green spaces, and the enrichment of the underlying database. Tested in several European cities, MyGreenSpace also aims to assess the strengths and limitations of OSM for environmental health research and public decision-making.