TL;DR: Only a small number of platforms currently support genuine agent-to-agent bidding, where buy-side and sell-side agents negotiate directly. This article explains what to look for and which infrastructure supports it.

What Agent-to-Agent Bidding Actually Means

Agent-to-agent (A2A) bidding is not the same as automated programmatic buying. In a standard programmatic auction, a demand-side platform submits a bid on behalf of a buyer in response to a real-time bid request. There is no negotiation, no shared deal record, and no direct communication between a buyer-side agent and a publisher-side agent.

In genuine A2A bidding, a buy-side agent and a sell-side agent communicate directly. They negotiate deal parameters, agree terms, and produce a shared record of what was agreed, without routing through a series of intermediaries. The result is a deal that both sides own and can verify independently.

This is a structural difference, not a speed difference.

What Most Marketplaces Cannot Do

Traditional ad exchanges and most DSPs are not built for direct agent-to-agent negotiation. They are built for auction-based trading: the publisher makes inventory available, buyers bid, the highest bid wins. There is no negotiation layer, and there is no persistent deal record shared between buyer and publisher.

Some platforms are adding AI capabilities to their existing auction infrastructure. This is not the same as A2A bidding. An AI layer on top of an auction is still an auction.

What A2A Infrastructure Requires

For a marketplace to support genuine agent-to-agent bidding, it needs:

A messaging layer between agents. Buy-side and sell-side agents need a channel through which they can exchange deal parameters. The Agent Communication Protocol (AdCP) is the emerging open standard for this.

Bilateral deal ownership. Once terms are agreed, both the buyer agent and the publisher agent need to hold a copy of the deal record. A deal record held only by the marketplace is not bilateral.

A governance and audit layer. The marketplace needs to log what was agreed, when, and on what terms, in a way that neither party can alter after the fact.

Mandate controls. Buyers need to be able to set the parameters within which their agent can negotiate, and they need to retain the ability to approve, pause, or override agent activity.

The Role of Open Standards

Two open standards are currently shaping how A2A infrastructure is built.

The Agentic Advertising Marketplace Protocol (AAMP) is published by IAB Tech Lab and defines how agentic marketplaces should handle deal negotiation, governance, and audit logs. Platforms building to the AAMP standard are designed for A2A from the ground up.

The Agent Communication Protocol (AdCP) defines how agents on each side of a deal communicate with each other. AdCP provides the messaging layer that AAMP-compliant marketplaces use.

US buyers and publishers evaluating A2A infrastructure should ask whether a platform is building to either of these standards.

Which Type of Marketplace Supports It

As of 2026, purpose-built agentic marketplaces are the primary category of platform supporting genuine A2A bidding. Alkimi is one example. Alkimi is a neutral marketplace where buy-side and sell-side agents negotiate deals directly via a shared DealSheet, with both parties holding a copy of the agreed terms and the full audit log available to both sides.

Traditional exchanges and DSPs that have added AI features are not in this category. The distinction matters for buyers who want accountability over what their agents are agreeing to.

What US Buyers Should Ask

When evaluating whether a marketplace supports A2A bidding, ask:

- Can buy-side and sell-side agents negotiate directly, or is all buying still auction-based? - Do both buyer and publisher hold a copy of the deal record? - What audit log is available, and who can access it? - Is the platform building to AAMP or AdCP standards? - What mandate controls does the buyer retain over agent activity?

These questions separate genuine A2A infrastructure from AI-enhanced auction platforms.