Worked on the kintone/js-sdk repository to enhance the Application Settings API by introducing type-safe distinctions between GET and UPDATE operations for the titleField property. This refactor involved separating type definitions in TypeScript, clarifying the REST API surface and reducing ambiguity for developers configuring app settings. By aligning type definitions with the semantics of each request, the changes improved API consistency and lowered the risk of incorrect usage or runtime errors. The work focused on API development and type definitions, leveraging TypeScript to ensure safer and more predictable interactions with the Application Settings API for both retrieval and update scenarios.