This paper develops and tests a new self-assessment policy tool that illuminates the quality of planning policy for green infrastructure (GI). Working with 19 local planning authorities within the UK Central Scotland Green Network area (CSGN), the multi-functional coverage and strength of GI policies in statutory development plans were assessed. The tool was built from fusing two existing but unrelated initiatives addressing GI standards; Building with Nature and Integrating Green Infrastructure (IGI). The results reveal surprising variation across the functional coverage of GI-related policy and strength of associated policy wording, suggesting a significant vulnerability for how GI is mainstreamed in decision-making processes. To address this knowledge exchange deficit, the best performing policies were captured and adapted to inform a suite of model policies with global application. Significantly, the policies champion the different functions performed by GI and stress the need for early and ongoing involvement throughout any development process with funding for long-term stewardship post-development. The results serve as a catalyst for improved dialogue and social learning across planning, and wider built/natural environment teams and professions to plug identified policy gaps. In particular, there is recognition of the need for planning policy responses to move outside their usual environmental remit and engage with other policy sectors using more holistic policy hooks such as placemaking, placekeeping and the climate emergency. We argue that this tool has universal applicability in many planning systems for improving the policy response and imperative for GI, thereby increasing the potential for better spatial planning delivery.