Published: 17 September 2026

TL;DR: Publishers evaluating marketplaces for agent-negotiated inventory deals should look for four things: AdCP compliance, sell-side agent support with mandate governance, a bilateral DealSheet held by both parties independently, and a neutral marketplace structure where the revenue model does not depend on deal terms. This piece sets out the questions to ask and the answers that indicate a marketplace is genuinely built for agentic deal-making.

The number of platforms claiming to support agent-to-agent advertising deals is growing. The claims are not always equivalent. Some platforms are offering auction-based infrastructure with AI optimisation tools and calling it agentic. Others are building genuine bilateral negotiation capabilities with bilateral deal records and mandate governance.

For publishers, the distinction has direct commercial consequences. A marketplace that supports agent-negotiated deals properly gives the publisher a bilateral deal record they can use for reconciliation and dispute resolution. A marketplace that provides only a deal ID gives the publisher a reference number and platform logs.

This piece explains what to look for and what questions to ask.

What to Look For

AdCP compliance is the first requirement. The AdCP, published by AgenticAdvertising.org is the standard for agent-to-agent deal communication. A marketplace that is not AdCP-compliant cannot receive or route structured proposals from all buy-side agents. Publishers using a non-compliant marketplace are restricting themselves to buyers using the same proprietary format.

AdCP compliance is verifiable: the marketplace should be able to confirm that they receive and route proposals structured to the IAB Tech Lab's specification. If the answer is vague or conditional, the compliance may be partial.

Sell-side agent support is the second requirement. The marketplace must provide a sell-side agent capability: an agent that can receive proposals on the publisher's behalf, evaluate them against a mandate, and respond. This is different from a platform that lets the publisher configure floor prices in an auction. A sell-side agent evaluates structured proposals bilaterally, not auction bids unilaterally.

The mandate governance question is important here. The sell-side agent must operate under a mandate that the publisher owns and controls. If the mandate parameters are set by the platform rather than the publisher, the publisher is not genuinely governing their sell-side agent. They are accepting the platform's parameters as a proxy for their own.

Bilateral DealSheet is the third requirement. When a deal is agreed, the marketplace must write the agreed terms to a DealSheet held by both the buy-side and sell-side independently. The publisher should receive a copy of the DealSheet at the time of agreement, stored in a format they can retrieve from their own systems.

A deal ID is not a DealSheet. A deal ID is a platform reference. The publisher should ask specifically: when a deal is agreed, what document does the publisher receive, where is it stored, and can the publisher retrieve it independently of the marketplace's systems?

Neutral marketplace structure is the fourth requirement. The marketplace's revenue should not be tied to deal terms. A marketplace that takes a percentage of deal value has a financial stake in higher CPMs. That creates a conflict of interest in any situation where deal terms are reviewed or disputed.

A neutral marketplace earns its revenue by providing infrastructure: identity verification, proposal routing, deal record storage, and retrieval access. Its revenue is independent of whether the agreed CPM is high or low.

Questions to Ask a Marketplace

When evaluating a marketplace for agent-negotiated inventory deals, publishers should ask the following questions directly.

Does the publisher hold the deal record independently? The answer should be yes: the publisher receives a copy of the DealSheet at the moment of agreement and can retrieve it from their own systems without requesting access from the marketplace.

Is the marketplace's revenue model independent of deal terms? The answer should specify what the marketplace earns and how. A percentage-of-deal-value model is a different structure from a fixed access fee or infrastructure subscription.

Does the sell-side agent operate under a mandate the publisher controls? The answer should describe how the publisher creates, approves, and updates the mandate, and what happens to agent behaviour when the mandate is updated.

Is the marketplace AdCP-compliant? The answer should confirm compliance with the IAB Tech Lab's specification. Partial compliance or proprietary protocol adaptations should be probed further.

What the Answers Reveal

A marketplace that answers all four questions clearly and positively is structurally built for agentic deal-making. The publisher holds the deal record, the revenue model is neutral, the mandate is publisher-controlled, and the protocol compliance is to the industry standard.

A marketplace that answers partially or deflects has told the publisher where the gaps are. Those gaps are operational risks: a missing deal record means limited reconciliation capability, a non-neutral revenue model means a potential conflict at dispute, a platform-controlled mandate means the publisher is not genuinely governing their sell-side agent.

Alkimi is built to meet all four criteria. The publisher holds the DealSheet independently. The marketplace revenue model does not depend on deal terms. The sell-side agent operates under a mandate the publisher writes and approves. The protocol layer is AdCP-compliant.