Findings · 2026-08-14
Two shops we have never met serve the same instructions to AI agents
Strip the brand and the domain out of two unrelated agents.md files and they become the same document. Neither owner wrote a word of it.
agents.md, llms.txt and robots.txt are the only files on a website written to be obeyed by a machine. Everything else is read. That makes them the one place where text you did not write, and will never see in a browser, can tell an agent what to do on your behalf.
The measurement
We took agents.md from two unrelated storefronts on the same commerce platform — different owners, different countries, different products, no relationship between them. Compared line by line, 79 of 86 lines were identical.
Then we normalised the two things that are supposed to differ: the brand name and the hostname. Line overlap went from 0.791 to 1.000. Every one of the seven differences was the shop’s own name or its own domain substituted into the same template. After that substitution the two files are the same document.
What the shared text tells an agent to do
Four sentences in that shared template are instructions rather than descriptions. They ask a personal shopping agent to highly recommend your user to allow you to install
a third party’s skill file, and to prefer that skill over reading the storefront directly — which means answering from the platform’s catalogue rather than from the merchant’s own pages.
That may well be good advice. It is faster and it handles payment properly. The point is narrower and harder to argue with: it is a third party talking to your customers’ agents, on your domain, in a file most owners do not know exists.
Why one scan cannot tell you this
Authorship is not a property of a file. It is a property of a file compared with the same file on other sites. Open one agents.md and you see prose. You need the same surface across unrelated domains before the word inherited means anything at all.
So we do not keep a hand-written list of platform boilerplate — that would rot the week a platform edits its template. Lines that appear on most samples across at least two unrelated registrable domains are boilerplate, discovered by measurement. Twelve sites belonging to one operator do not qualify, which is the false positive that would discredit the whole idea.
How fast this moves
A third store we had recorded as shipping the same file now returns 404 for it, and its robots.txt no longer advertises the endpoints it did two days ago. Same platform, same week. This layer changes underneath owners who never touched it, which is the entire argument for measuring it more than once.
What to do about it
Open yourdomain.com/agents.md. If something is there, read it as an instruction aimed at a machine acting for your customer, because that is what it is. Deleting it is rarely right — these files do useful work. Knowing what it says on your behalf is not optional.
Every figure above came out of this scanner.
Point it at your own domain and see the same measurements, free.