Problem:
When a tool throws an McpError with a data payload for structured error context, the server's error handler correctly catches the error but only includes the code and message in the final JSON-RPC response. The data field is ignored and not sent to the client.

This limits the ability to provide rich, machine-readable error context from tools as intended by the JSON-RPC specification.

To Reproduce:
Create a tool that throws an McpError with a data payload:

  throw new McpError(
    ErrorCode.InvalidParams,
    'Invalid parameters provided.',
    {
      'field': 'experienceId',
      'issue': 'The experience ID is not valid.',
    }
  );
});

Expected Outcome:

{
  "jsonrpc": "2.0",
  "error": {
    "code": -32602,
    "message": "Invalid parameters provided.",
    "data": {
      "field": "experienceId",
      "issue": "The experience ID is not valid."
    }
  },
  "id": "1"
}

Actual Outcome:

{
  "type": "text",
  "text": "MCP error -32602: Invalid parameters provided."
}