Developed certificate-based authentication via mutual TLS for the google-auth-library-python repository, focusing on enhancing backend security and API integration. The implementation introduced dynamic IAM endpoint selection, allowing the library to automatically determine when to use mTLS based on environment variables. This approach ensures that secure endpoints are consistently applied in varying deployment contexts. Additionally, support was added for an alternative environment variable, enabling users to control mTLS usage through Gcloud CLI configuration. The work leveraged Python and emphasized backend development and security best practices, resulting in a more flexible and robust authentication mechanism aligned with enterprise cloud requirements and standards.