Webhook

An HTTP endpoint that receives an event message from another service, allowing an application to react without repeatedly polling for changes.

With a webhook, one service sends an HTTP request to an address you register when a selected event occurs, such as a pull request opening or a payment completing. The receiving application verifies the request, records its event identifier, acknowledges delivery, and starts the relevant workflow. Delivery can be delayed, duplicated, retried, or arrive out of order, so 'instant' and 'exactly once' are not safe assumptions.

Builder example

Webhooks reduce polling delay and empty checks, but they create an internet-facing input boundary. Verify the provider's cryptographic signature before generated content reaches the agent, reject stale requests when the protocol supports timestamps, deduplicate event identifiers, and make handlers idempotent. Queue longer work so the endpoint can acknowledge within the provider's timeout.

Common confusion: A webhook starts your agent when an event happens elsewhere, while a cron schedule starts it at a fixed clock time no matter what changed. Reach for a webhook when the work must follow an event closely, and a cron schedule when a steady, predictable rhythm matters more than instant response.