Cursor MCP Test Server

This is a minimal MCP server designed to reproduce the issue where Cursor Desktop incorrectly rejects valid values for optional parameters that use JSON Schema union types (e.g., ["null", "string"]).

Reproducing

1. build the MCP server with go build
2. add cursor-mcp-test to registered servers ~/.cursor/mcp.go:

{
  "mcpServers": {
    "cursor-mcp-test": {
      "command": "/absolute/path/to/cursor-mcp-test"
    }
  }
}

3. Restart Cursor and ask it to invoke the server's "Example Tool"