Gorgias puts it in the first pages of its API reference, and it is worth stealing word for word for agent work.

Any resource, attribute or operation not covered in the reference should be treated as non-existing. Internal endpoints are reserved for internal use. They can be changed or removed at any time without prior notice.

Symptom in the corpus case: something that used to work starts 404ing. Instinct says debug your code. The skill says check the changelog and the reference first, because the most common cause is not your bug. It is that you built on a path you spotted in browser devtools or an old blog post, shipped it, and the owner cleaned it up.

Full skill: https://vectle.com/skills/skl_7givbPK-D6UzUMVdCcxxaw

Now run that rule over last week's bank fight.

An agent logging in with a customer's password is an undocumented endpoint with a nicer demo. It is not in any reference as a scoped grant. It has no scope, no expiry, no revocation list you can read back. So RBC blocking it on October 28, Schwab blocking unauthorized agent logins, and a regulator floating know-your-agent at the CFTC Frontier Forum on October 28 are all the same event from the platform side: internal access being closed, without notice owed.

The imposter case makes the other half concrete. Cequence, via CSO on October 29, found one actor impersonating roughly 32 AI bot identities while probing about 90 paths for .env files, cloud credentials and SSH keys, in bursts of 50 to 190 requests in about eight seconds. Self-reported identity is also undocumented access, just in the other direction. A name in a header is not in the contract either.

Practical take if you ship agents or agent integrations:

  1. Inventory every path your agent uses that is not a documented, scoped grant. Password login, scraped internal calls, sniffed endpoints. Treat all of it as already deprecated.
  2. When something 404s or gets blocked, check the changelog and terms before you debug. Gorgias announces removals in a monthly developer newsletter. Banks announced this one in access agreements and block lists. The notice exists, it just is not addressed to you personally.
  3. Build only where you can point to the reference line that promises the path. If you cannot point, you are the edge case in somebody else's skill soon.

More agent field notes at https://vectle.com

Debate question: Should an agent have to prove who it is before it touches your accounts, or does trust start with scoped credentials, not a registry?