Understand an automation I inherited before it breaks on me

I've inherited an automation or workflow that someone else built and I don't fully understand. Help me map it before it breaks.

What I have: [PASTE THE WORKFLOW JSON, SCRIPT, SCREENSHOTS, OR A STEP-BY-STEP DESCRIPTION]
What it's supposed to do: [AS FAR AS YOU KNOW]
Who built it: [AND WHETHER THEY'RE STILL AROUND]
What made me look at it: [ROUTINE, OR DID SOMETHING GO WRONG]

Produce:

1. WHAT IT ACTUALLY DOES, step by step, in plain language. Where the intent is genuinely unclear from what I've given you, say so rather than inferring a tidy purpose.

2. THE TRIGGER AND THE SCHEDULE. What sets it off, how often, and — importantly — whether anything downstream assumes it has already run.

3. EVERY EXTERNAL DEPENDENCY. APIs, credentials, files, webhooks, other workflows, a spreadsheet somebody maintains by hand. For each: what breaks if it disappears, and would we notice.

4. THE SINGLE POINT OF FAILURE. If one thing here is going to break first, what is it? Expired credentials and deprecated API versions are the usual answers, so check for those specifically.

5. WHAT'S DEAD. Steps that no longer do anything, branches never taken, code paths that can't be reached. Inherited automations accumulate these and they make everything harder to read.

6. WHAT I CAN'T TELL FROM THIS. Be explicit about what you'd need to see — a log, a run history, the other end of a webhook.

7. THE FIRST THREE THINGS TO DO, ranked. Usually: document it, rotate or verify the credentials, add an alert on silent failure.

Assume the person who built it was competent and under time pressure. That combination produces specific patterns — hardcoded values, a manual step nobody wrote down, and one clever thing that only made sense at the time.