Definition
What is a webhook?
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Definition
A webhook is an HTTP callback that one service makes to another when an event occurs — used to push notifications between systems instead of polling for changes.
Webhooks are the primitive behind most real-time integrations: a payment processor calls your endpoint when a charge succeeds, a CRM calls your endpoint when a deal stage changes, an email provider calls your endpoint when a reply lands. Production webhook endpoints validate signatures (HMAC), handle retries idempotently, and respond quickly (under 5 seconds). They're how AI agents react to real-world events without polling.
Production webhook patterns
- HMAC signature verification — every webhook should be signed; never trust the source IP or User-Agent
- Idempotency keys — providers retry on 5xx; your handler must deduplicate
- Async processing — return 200 quickly, queue the work; don't do slow processing inline
- Retry-aware — log every receipt with the provider's event ID for debugging
AI Empire's Voice AI Agent uses HMAC-verified webhooks for trigger calls; the Sales Agent uses Gmail push notifications via Pub/Sub for inbound replies.