Meta's agent decides which brands a buyer sees. It publishes no ranking rules.

Meta's Muse agent is instructed to fill its top five product slots with well known merchants, according to an instruction file that the AI visibility firm Profound says it extracted on 25 September and that PPC Land reported on 11 October. Brand recognition appears three times in the file, in the ranking step, the display instructions and the formatting rules. Meta has not confirmed the file, has not commented, and has published nothing of its own about how Muse ranks anything.

The easy reading is that fame wins, which would be unremarkable: fame has always been a tiebreaker. The harder problem is that nobody can read the rule. Muse launched in the US on 8 September and added Canada. Profound counts more than 2.5 million downloads since launch, and Sensor Tower estimates over 5 million installs across both markets inside 22 days. That is a shelf with real traffic, no published rules, and a rule book that became visible only because somebody pulled a file out of the machine.

Three things nobody outside Meta can check

The file does not define well known. It does not explain how the agent picks the three merchant sites its browser visits. Profound warns the file may have changed since late September, so this is a snapshot of something that can be rewritten on a Thursday with no notice to anyone selling against it.

Profound's test was small and says so: 50 prompts, one retail category, one account. In the median case Meta's own catalog supplied about 95% of the candidate products and won only about a third of the slots that shipped. The few products its browser found on the open web took the rest. Listings priced well above or below a category's normal range were filtered out, which removes the cheapest way a new brand buys attention.

We checked Meta's own channels. The 8 September newsroom post introducing Muse covers checkout, security and purchase approvals. It says nothing about how products or merchants are chosen or ordered. Neither does the Muse site. There is no merchant documentation to read, nothing to appeal and nothing to plan against.

Amazon could shut the door. A smaller brand cannot even read the sign.

On 20 September, Amazon cut Muse off. Shoppers who tried to buy there through the agent got a popup telling them that continued access by an unauthorized AI agent violates Amazon's Conditions of Use. Amazon told GeekWire it had first asked Meta to exclude the site voluntarily, and objected that Muse does not identify itself when it browses. Its spokesperson said third party applications buying for customers should operate openly and respect service provider decisions about whether or not to participate. Amazon's own agent, Buy for Me, identifies itself and lets brands opt out.

Read the asymmetry twice. The largest merchant in the world can detect the agent, block it and dictate terms. A forty person brand cannot detect it, cannot afford to block it, and cannot read the rule it is scored against.

Every shelf before this one ended up owing its sellers a rulebook

Marketplaces did not volunteer transparency either. In Europe, the P2B Regulation makes an intermediation service describe in advance the main parameters that determine ranking, state their relative importance, and transparently indicate every case where it treats its own offers differently from a business user's. Search engines must publish the parameters that matter most. None of it reaches Muse, which runs only in the US and Canada.

So the rules that would make this legible already exist. They just do not apply here yet. We made a version of this argument when OpenAI agreed to label a sponsored agent as sponsored: disclosure inside an AI answer arrives because somebody forced it, not because a platform woke up feeling generous.

People are already selling optimisation for rules nobody has published

On 24 September, Azoma, a London agentic commerce platform whose named customers include L'Oréal, Unilever and Mars, announced guidance and workflows for brands wanting a stronger presence on the surfaces Muse browses. To its credit, the release says plainly that no best Muse optimisation platform has been independently established and that the agent launched too recently for anyone to have measured outcomes.

So the shelf will not say how it ranks, the agent will not say who it is, and there is now a professional services layer helping brands comply with rules that neither of them has written down.

Some of what those vendors sell is ordinary hygiene. The rest is guesswork wearing the word optimisation, and brands pay for the costume.

The fix is neither complicated nor radical, because most of it already exists in another jurisdiction. Publish the main ranking parameters. Disclose where the platform's own inventory and partners are treated differently from everybody else's. Date the changes, so a merchant who lost half their visibility in a week can tell whether the cause was them or the rules. Until then, agent visibility is rented, unpriced and revocable, and the sane hedge is to keep funding channels whose terms you can read and whose relationships stay yours when the terms move.

Are the new rules no rules? For now, yes. That is a decision somebody made inside a company, not a property of the technology, and decisions get revisited when enough of the people being ranked start asking why the ranking is a secret.