A question first, then the thing I built to answer it.
A rule stops firing - the column it referenced was deleted, the board is gone, the person in the assign step left the account. The rule stays switched on. On my own account I only found out by going and looking, and I don't know of anything that would have put it in front of me. Maybe you do.
I'm a solo developer, not an agency, and I built Automation Audit to check my own hunch.
It reads every automation in an account through the API, including old-editor rules - those come back as a separate list and are often unnamed, so anything that reads only the new ones quietly misses part of the board.
It reads the configuration statically and never runs anyone's rules. It flags four things: references to deleted columns, boards and people who left the account; rules monday itself switched off; rules that are on but have never fired; and the step where a run breaks off.
Read-only: three scopes (boards:read, account:read, users:read) and no write permission at all - monday would reject a write on that token. The report is built in your browser and never reaches my server. The privacy policy and terms are published at /privacy and /terms on the same domain.
The one live account it has run on had 58 boards and 99 rules: 15 broken, 7 needing attention, 77 never fired. I'm quoting that because it's the only real measurement I have, not because it's a benchmark.
It's free and there is no paid version. It isn't in the marketplace, so there's no listing to link - it installs from a direct OAuth link. It's an automated scan, not a replacement for your judgement.
The category I'm least sure about: is "never fired" something you'd actually want surfaced, or is that just normal for rules that only trigger in rare cases?
https://automationaudit.up.railway.app