tsd is a TypeScript Definition (TSD) manager, streamlining the process of searching, installing, and managing TypeScript declaration files for JavaScript libraries within your projects. It simplifies dependency management for TypeScript projects by providing a central repository and intuitive commands to handle type definitions. TSD aids in ensuring type safety and enhances the development experience when working with JavaScript libraries in TypeScript environments. It predates the functionalities offered by @types and npm integration for type definition management.