Developed and delivered HVAC system interface updates for the lsst-ts/ts_xml repository, focusing on expanding commands, events, and telemetry to enhance subsystem control and observability. The work involved designing and implementing new API endpoints and updating interface definitions, with careful attention to maintaining API stability and compatibility with existing telemetry pipelines. Comprehensive documentation was created to support both maintainers and users, ensuring clarity around the interface changes. The updates were integrated through a pull request workflow, validated by continuous integration checks, and merged into the main codebase. Skills demonstrated include Python, XML schema design, and API-driven development practices.