Markus Kusano contributed to the modelcontextprotocol/go-sdk repository by developing default value support within elicitation schemas and enhancing schema validation logic. Using Go and the jsonschema library, he implemented comprehensive validation for multiple data types and ensured that defaults are correctly applied to elicitation results. Markus also expanded and refined the test suite, focusing on validating elicitation handler content against defined schemas to prevent invalid data from passing through the pipeline. His work improved the reliability and robustness of the backend, strengthened CI confidence, and laid a solid foundation for future schema enhancements by addressing validation gaps and surfacing errors early.