The Incoming Webhook trigger allows you to trigger a rule's execution by sending a HTTP GET request to a URL. This give a generic way to run a rule from custom scripts, third party services, or any other source that can send a HTTP request.
Before creating a rule with this trigger, you will need to set up a webhook URL. This can be done by clicking the Add Incoming Webhook button on the Integrations page.
Select the webhook you want to use to trigger the rule.