ERR_NGROK_402: Only the first part of a reserved domain may be a '*' wildcard

What does ERR_NGROK_402 mean?

ngrok returns ERR_NGROK_402 with this message:

Only the first part of a reserved domain may be a '*' wildcard. Failed to reserve <DOMAIN>.

Troubleshoot ERR_NGROK_402 with your AI agent. Connect it to the ngrok MCP server, then ask what caused the error and how to fix it.

Email support@ngrok.com and include the error code.