Chaitanya Phadke enhanced the UKHO/s-100-permit-service repository by refactoring its OpenAPI specification to improve API contract clarity and client resilience. He migrated response definitions to component references and introduced a 429 Too Many Requests response, addressing integration reliability and error handling. Using YAML and leveraging skills in API Design and OpenAPI Specification, Chaitanya clarified error messaging for BadRequest and TooManyRequests scenarios, reducing ambiguity for API consumers. He also documented the use of the origin header with explicit examples, ensuring consistency across responses. The work focused on maintainability and traceability, laying a foundation for future improvements in API robustness.