Worked on enhancing the security and reliability of the modelcontextprotocol/rust-sdk by addressing a critical issue where sensitive credentials could be exposed in Debug output. Utilized Rust and backend development skills to replace derive(Debug) with manual Debug implementations for credential types, ensuring that access tokens, refresh tokens, and other secrets are redacted. Developed comprehensive regression tests to validate that no plaintext secrets are emitted during debugging. Updated authentication-related code paths to support these changes, improving both code quality and test coverage. This work laid the foundation for ongoing security hardening and contributed to a more robust and maintainable Rust SDK.