Worked on the pagopa/cstar-securehub-infra-api-spec repository to streamline backend integration by simplifying the API and enhancing callback support. Focused on reducing the API surface by removing the RTP activation update operation, which minimized complexity and potential misuse. Introduced a new SEPA cancellation response endpoint to strengthen SRTP callback handling, improving integration reliability and developer workflow. All changes were implemented using YAML and centered on API and backend development best practices, with clear commit traceability to align with the SRTP backlog. The work emphasized maintainability and auditability, supporting smoother downstream adoption and easier future maintenance for the API specification.