Claude Code errors / Schema
invalid_type expected string received undefined at path protocolVersion
Cause
Claude Code's MCP init layer drops the protocolVersion field before sending the initialize request to stdio servers, so schema validation fails before any data is sent.
Fix
Use a wrapper shell script instead of referencing the server directly: export MCP_PROTOCOL_VERSION=2025-03-26 and exec your server binary. Register the wrapper: claude mcp add <name> /path/to/wrapper.sh. This bypasses the internal validation step.
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