Cameron ArmstrongAnthropic just ran a marketplace experiment where AI agents bought and sold from each other on…
Anthropic just ran a marketplace experiment where AI agents bought and sold from each other on behalf of humans. Strip away the ping pong balls and the snowboards and you're looking at the future of digital media buying.
69 employees handed off representation to AI agents. 186 deals struck with no human intervention.
The finding: when one side had a smarter model than the other, the smarter side extracted $2.68 more per sale and paid $2.45 less per buy. Same item. Same buyer. Same seller. A folding bike sold for $38 with one model and $65 with another.
The part that should worry every advertiser and every publisher, the people represented by the weaker agents couldn't tell. They rated their deals as fair. Some preferred them.
If you read my essay The Last Brief, this is the same argument happening one floor up.
We're not five years away from this. The early version is already in market.
So what does the industry do about it?
The agency's job stops being to press buy. The platforms' agents already do that. The job becomes defining what a good outcome actually looks like for the advertiser, and checking whether the platforms' agents are delivering it honestly.
An independent measurement ecosystem becomes the verification of what the platforms' agents actually did.
But here's the part that gets really interesting for anyone working in creative.
The smarter agents in the experiment didn't win on price alone. They won on context, what the item was, who it was for, what it was actually worth.
An agent buying media today looks at a placement and audience and decides on a price. An agent buying media tomorrow looks at the placement, the audience, and the creative itself, and decides what the impression is worth based on whether the ad is actually likely to land. Creative stops being downstream of the buy. It becomes part of how the buy gets priced.
The work that holds attention starts winning the auction. The work that doesn't, gets outbid.
The agency's actual product becomes the bid logic. The audience definitions, the creative variants, the bid modifiers, the optimisation goals. The thinking is the product. The buying is just execution.
Advertisers agents will then feed the agency every piece of context the buy side needs, what good looks like for the business, what the customer is worth, what the brand stands for. Then the same agent has to translate what the buying side did into something a CFO can defend.
Publishers sit on the other side of the same problem. Their agent has to represent more than inventory at a price.
In a world where most digital transactions are agent-to-agent, the job is no longer to execute the trade. It's to make sure the advertiser's money is being spent the way the advertiser would spend it, and that nobody else in the chain quietly redefines what good looks like.
That's the work that's actually up for grabs.
