What is the right format of webhook?

Hi opsnull,

Thank you for bringing this to our attention. This is a bug on our side, and I have filed a issue on github.

As you can see the validation takes place here in the kibana plugin:

A workaround for now would be to use the API rather than Kibana. Let me know if you need any assistance putting that together :slight_smile:

This issues has been fixed.