Webhook

What is a webhook?

Say you’re expecting a parcel. You could go down to the front door every ten minutes to check, or leave your number so the courier rings you. The first approach is like polling an API over and over. The second is a webhook: the system that has the news tells you as soon as it happens.

Technically, a webhook is an HTTP call, nearly always a POST, that a service sends to a URL you gave it. It carries a small data payload describing the event. Your system receives it, replies “got it” and acts on it.

How it works

1. Subscribe. In the source service you choose the events you care about (message received, payment confirmed, call ended) and the URL to notify.
2. Event. When something happens, the service sends a JSON payload to that URL.
3. Quick reply. Your system acknowledges with a 200 status. If it doesn’t, the sender usually retries.
4. Action. Using the data, your system does whatever is needed: create a record, send an email, start a workflow.

A typical payload looks like this:

{
  "event": "appointment.created",
  "occurred_at": "2026-10-07T09:30:00Z",
  "data": { "customer": "Sarah Jones", "service": "Check-up" }
}

Two basic precautions: verify the signature, and don’t process the same event twice if it arrives more than once.

Don’t confuse webhooks with their neighbours. An API waits to be asked. MCP and function calling let an AI model use tools when it decides to. A webhook runs the other way: the outside world wakes your system up.

Example

A driving school in Manchester uses an online booking tool. Every time someone books a lesson, the tool fires a webhook. A small AI automation workflow picks it up, writes a welcome message with the date and the instructor’s name and saves it to the learner’s record. Before, someone in the office checked bookings twice a day.

How it affects your business

Webhooks are the glue between tools. If you want an AI agent to react to what happens in your online shop, your calendar or your ERP, something has to tell it, and this is the usual way.

At UTIO, the AI API is the other half of that exchange: your system receives the notification, then calls the API to transcribe audio, generate text or send a message by WhatsApp, voice or email. Calls that send through a channel require an Idempotency-Key header, so if your workflow retries because a webhook arrived twice, the customer doesn’t get the message twice.