A buyer agent wants to spend on a recipe site. Before it sends a single offer it has to answer one question, the same question a careful buyer has always asked: who is actually allowed to sell this site’s inventory? Get that wrong and you are paying a stranger.
You met this exact question in Track C. A publisher declares its authorized sellers in ads.txt, and a buyer verifies them against each SSP’s sellers.json. The agentic world needs the same trust layer, one level up: a way to declare which agents may sell a property.
adagents.json: ads.txt for agents
A property owner publishes an adagents.json file that lists the sales agents authorized to represent its properties. A buyer agent reads it to discover who it can legitimately deal with, then queries those agents for availability. It is the agentic counterpart of ads.txt: a public, machine-readable declaration of "these parties may sell on my behalf."
| Question | Header-bidding answer | Agentic answer |
|---|---|---|
| Who may sell this inventory? | ads.txt (authorized sellers) | adagents.json (authorized sales agents) |
| Is that party who they claim? | sellers.json reciprocity | Agent identity and registry checks |
| How deep is the chain? | schain nodes and hops | The agents and systems in the path |
- 1Discover: read the property’s adagents.json to find authorized sales agents.
- 2Verify: confirm each agent’s identity, ideally against a shared registry.
- 3Query: ask the trusted agents what is available and at what price.
- 4Approve: route anything that needs a human (budget, brand safety) for sign-off.
- 5Execute: place the buy through an authorized agent only.
Watch out
An agent offering to sell a property that does not list it in adagents.json is the agentic version of an unauthorized reseller in ads.txt. It is exactly the kind of path the Bidcliq audit flags today, and the reason discovery has to come before the deal.
Key idea
Automation does not remove the human, it relocates them. People still set budgets and guardrails and approve sensitive steps. Brand safety and fraud control move from manual review to rules the agent enforces, with a person on the exceptions.
Quick check
A buyer agent is offered premium inventory by an agent that does not appear in the property’s adagents.json. What should it do, and what header-bidding red flag is this like?