Worked on the BitGoJS repository to enhance API consistency by refactoring AddressBook GET endpoints to accept filtering criteria via URL query parameters, aligning with RESTful standards. This update replaced the use of request bodies with query parameters for methods such as getConnections, getListingEntryContacts, and getListingEntryDirectory, reducing API payloads and improving client integration. Comprehensive unit tests were developed using TypeScript, Sinon, and Superagent to ensure correct serialization and handling of query parameters. The work not only improved test coverage but also established a foundation for future analytics and observability, reflecting a methodical approach to scalable API development and maintenance.