Worked on the modelcontextprotocol/kotlin-sdk repository to implement MCP extension negotiation during the initialize handshake, enabling both clients and servers to advertise supported protocol extensions through a new extensions field in their capabilities objects. This enhancement, developed in Kotlin, focused on increasing interoperability and extensibility within the protocol. The approach included comprehensive unit testing to validate the negotiation flow and ensure alignment with the MCP specification, as well as thorough updates to documentation and release notes to support downstream users. Emphasized API development, JSON handling, and test-driven development practices, resulting in a robust, forward-compatible protocol extension for the Kotlin SDK.