The Lives Saved Tool (LiST) is a widely used software package for modelling changes in child, neonatal, and maternal mortality. Until recently, it has mainly been used as a standalone tool that people manipulate using its desktop or online interface. The developers of LiST have now created a web-based application programming interface (API) allowing other software programmes to interact directly with LiST to use its internal calculations. This opens the door for using LiST within more complex models, for which coverage-to-mortality calculations are only a part, or for building topic-specific tools with a custom interface. The API also allows other software programmes to access the data that has been gathered and maintained by the LiST team on the effectiveness and coverage of 70+ interventions, along with data on mortality rates, cause-of-death structures, and child nutritional status in low- and middle-income countries. In this viewpoint, we describe how we see the API being used and give examples of tools that are already using it. Our hope is that others can now take full advantage of LiST and its 20+ years of development to build their own tools for effective data use in global health.