Alerts

A monitor can tell you about changes in two ways. You can use both on one monitor, or neither and read the checks yourself.

Webhooks

With a webhook, two events are posted to you:

Event	When
`monitor.page`	A page changed, appeared, was removed, or started failing, and, with a goal, the judge ruled it meaningful
`monitor.check.completed`	A check finished, with its summary counts

{
  "webhook": {
    "url": "https://you.example.org/hooks/prefetch",
    "headers": { "Authorization": "Bearer your-token" },
    "metadata": { "env": "production" },
    "events": ["monitor.page"]
  }
}

The URL must use https://. Every request is signed with the monitor’s webhook.secret. Answer 2xx within 10 seconds. Failures are retried after 1, 5 and 15 minutes. See Webhooks for signature verification. A page that fails sends one monitor.page event, when it starts failing. Set notify_errors_after (1 to 10) to send it only once a page has failed that many checks in a row, so a site that blips once and recovers sends nothing.

Email

Add email to have changes emailed to up to 5 addresses:

{ "email": { "to": ["[email protected]", "[email protected]"] } }

Each check that finds changes sends one email to every active address. It lists the pages that changed, appeared or were removed, with the judge’s reason and the changed lines or fields. Up to 20 pages are listed, and the rest are counted. The same rules as the monitor.page webhook decide what counts. The baseline is never emailed, and with a goal, changes ruled not meaningful are left out. A page that fails to load is counted in the email, not emailed on its own. Emails are free. They never cost credits.

Confirming addresses

Each address has to agree to the emails before anything is sent:

Address	What happens
The email on your Prefetch account, or anyone’s in your organization	`active` straight away
Any other address	Gets one confirmation email, and stays `pending` until its owner selects Confirm. The link expires after 7 days.

Every email has an unsubscribe link, and supports one-click unsubscribe in mail clients that offer it. An address that unsubscribes shows as unsubscribed and gets nothing more from that monitor, even if you keep it in the list. To ask it again, remove the address and add it back. email.recipients in the response shows each address’s status. If a pending address never got its confirmation, send it again with a PATCH:

{ "email": { "to": ["[email protected]"], "resend_confirmation": true } }

An address can be asked to confirm at most 3 times a day, from any number of monitors, and one API key can send at most 20 confirmation emails a day. A request over either limit is refused with 429 and changes nothing.

Reading changes yourself

Without a webhook or email, read each check with GET /monitor/{id}/checks/{checkId}, or list recent checks with GET /monitor/{id}/checks. Over MCP, prefetch_get_monitor_check shows the latest check.

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Agents and MCP

Company data

Web data

Jobs and monitoring

Platform

Going to production

Webhooks

Email

Confirming addresses

Reading changes yourself

​Webhooks

​Email

​Confirming addresses

​Reading changes yourself

Webhooks

Email

Confirming addresses

Reading changes yourself