Worked on the DefinitelyTyped repository to enhance the Leaflet type definitions by making the radius property in CircleMarkerOptions optional. This change allowed developers to create CircleMarker instances without specifying a radius, reducing boilerplate and minimizing the risk of runtime errors related to missing values. The implementation involved updating TypeScript type definitions and corresponding tests to ensure strict type safety was maintained. Focused on API design and type definition best practices, the work improved maintainability and streamlined the developer experience for consumers of the Leaflet typings. The contribution demonstrated careful attention to both usability and robust type checking in TypeScript.