Worked on the UnionInternationalCheminsdeFer/OSDM repository to deliver two targeted API enhancements over two months, focusing on improving ancillary service handling within booking systems. Leveraging YAML for schema definition and API specification, introduced a reservations link to the ancillary object in offers, enabling direct association of reservation details with ancillary services and supporting smoother downstream integrations. Later, implemented an AncillarySubType schema and a subType field, allowing for more granular categorization of ancillary services to support analytics and future filtering logic. The work emphasized disciplined API design, careful schema evolution, and alignment with cross-team requirements to support partner onboarding and data integrity.