What a check costs
Creating, reading, changing and deleting a monitor is free. Each check is billed to the API key that created the monitor:
Pages that fail to load are never charged, and neither are skipped checks.
estimated_credits_per_check and estimated_credits_per_month on every monitor are upper bounds: they assume every page is fetched and judged on every check. actual_credits on a finished check is what you paid.
For example, a check of 18 pages where one page tracks json and changed, and 3 pages were judged, costs 18 + 3 + 3 = 24 credits.
When credits run out
A check never spends more than its key has left. If credits run out partway, the check stops and reportspartial. If the key has none at all, the check is recorded as skipped_no_credits, and the monitor keeps its schedule and resumes as soon as credits refill.
Automatic pausing
A monitor whose every page has failed for 10 checks in a row, over at least 24 hours, is paused, and its email recipients are told. Failed pages are never billed, so this only stops it retrying a page that’s gone or blocks every fetch. Setstatus back to "active" once the pages load.
Limits
The rest depend on your plan:
A request that asks for more than your plan allows is refused, and the error names the limit.
A monitor made on a bigger plan keeps running after a downgrade. A schedule that’s now too frequent moves to the fastest your plan allows, and its email recipients are told once. Its history is cut to your plan’s window.
A check that runs longer than 30 minutes stops and reports
partial.