Writing a tiny MCP server — registries, dispatch, and the response shape — step 6 of 9

Cursor wrote a call_tool dispatcher. When the handler raises an exception, the dispatcher returns just the exception's string — not an MCP error envelope. The client has no way to tell this was an error vs. a normal result.

Fix line 11 so that on exception, the dispatcher returns the proper MCP error shape:

{"isError": True, "content": [{"type": "text", "text": str(e)}]}

Expected output:

True
boom