Worked on the modelcontextprotocol/rust-sdk repository to enhance OAuth client authentication by implementing support for multiple token endpoint authentication methods. Focused on robust API integration and OAuth flows using Rust, the developer refactored configuration logic to automatically derive authentication methods from server metadata, reducing manual setup and minimizing errors with providers such as HubSpot. Expanded test coverage ensured correct behavior across supported authentication methods, following RFC 6749 guidance. Improvements included reading authentication method support from additional fields and establishing sensible defaults when metadata was missing. Code quality was maintained through consistent formatting and detailed commit documentation throughout the development process.