Published: 17 September 2026

TL;DR: AdCP is a protocol standard published by AgenticAdvertising.org. It defines how buy-side and sell-side agents communicate to negotiate a bilateral deal: the message format, the deal proposal schema, and the negotiation sequence. Alkimi is a marketplace: it provides the infrastructure that makes AdCP-compliant transactions possible between buyers and publishers who may not have worked together before. They are complementary, not competing. A buyer needs AdCP compliance to negotiate with any compliant sell-side agent. They need a marketplace like Alkimi to have a credible, neutral place to do it.

The distinction between a protocol standard and a marketplace platform is not always obvious in advertising technology. OpenRTB is a protocol. DoubleClick was an ad server. The two coexist: the protocol defines how systems communicate; the platform provides the infrastructure where that communication happens. The same relationship holds between AdCP and Alkimi.

What AdCP Is

AdCP (Agent Communication Protocol) is a standard published by IAB Tech Lab. It defines four things:

Identity verification format. How agents prove they are authorised to represent the organisations they claim to represent before any negotiation begins.

Proposal schema. The structure of a deal proposal: what fields it contains, what format those fields take, and what values are valid. A buy-side agent that submits an AdCP-compliant proposal is submitting a document that any AdCP-compliant sell-side agent can parse and evaluate.

Negotiation sequence. The defined message types that govern the negotiation: proposal, counter-proposal, acceptance, rejection. Both agents know what each message type means and what response options are available.

Deal record format. The structure of the DealSheet that is written when two agents reach agreement: what fields it contains, what format they take, and how the record is signed by both parties.

AdCP does not provide identity verification infrastructure, deal record storage, or neutral hosting for negotiations. It defines the formats and sequences. Implementation is the responsibility of the platforms that adopt it.

What Alkimi Is

Alkimi is a neutral agentic marketplace. It provides the infrastructure that makes AdCP-compliant negotiations possible at scale between buyers and publishers who may not have pre-existing technical integrations.

Identity verification infrastructure. When a buy-side agent connects to Alkimi to begin a negotiation, Alkimi verifies that the agent is authorised by the buying organisation it represents. When a sell-side agent connects, Alkimi verifies it represents the publisher it claims to represent. Both verifications use the identity format AdCP specifies. Alkimi provides the infrastructure that makes those verifications possible.

Deal record storage. When two agents reach agreement and write a DealSheet in the AdCP-specified format, Alkimi holds that record in shared state. Both parties can retrieve it independently. Alkimi provides the storage infrastructure that the DealSheet format requires.

Neutral hosting. A buy-side agent and a sell-side agent that have never interacted before can negotiate through Alkimi because Alkimi is a neutral party that both sides trust. The marketplace does not represent either buyer or publisher. It provides the venue where AdCP-compliant agents can meet and transact.

Why They Are Not in Competition

AdCP and Alkimi are not in competition because they operate at different layers. AdCP defines the communication standard. Alkimi provides the infrastructure. A buy-side agent that is AdCP-compliant can negotiate with any AdCP-compliant sell-side agent. To do that negotiation with a publisher they have not worked with before, they need a marketplace that both parties trust.

The parallel in conventional programmatic is OpenRTB and an SSP. OpenRTB defines the bid request format. An SSP provides the infrastructure where OpenRTB-compliant DSPs can access publisher inventory. A DSP being OpenRTB-compliant does not mean it can access a publisher's inventory without the SSP. The compliance is the prerequisite; the platform is the infrastructure.

For agentic advertising: AdCP compliance is the prerequisite. The marketplace is the infrastructure.

What a Buyer Needs to Get Started

A buyer who wants to use agent-to-agent deal negotiation needs two things.

First: a buy-side agent that is AdCP-compliant. This means the agent can submit proposals in the correct schema, interpret counter-proposals and rejections correctly, and write DealSheets in the correct format when deals are agreed. Without AdCP compliance, the agent cannot negotiate with AdCP-compliant sell-side agents, regardless of which marketplace it connects to.

Second: access to a marketplace like Alkimi that provides identity verification, deal record storage, and neutral hosting for AdCP-compliant negotiations. Without the marketplace infrastructure, the AdCP-compliant agent has nowhere to conduct negotiations with publishers it has not already integrated with directly.

What AdCP Compliance Signals

A buy-side agent that is AdCP-compliant can negotiate with any AdCP-compliant sell-side agent on any AdCP-compliant marketplace. This is the same portability that OpenRTB created for auction-based programmatic: a DSP that is OpenRTB-compliant can access any OpenRTB-compliant SSP without bespoke integration.

AdCP compliance for agentic advertising means buyers are not locked to a single sell-side agent or a single marketplace. If a publisher moves to a different marketplace, or builds their own AdCP-compliant sell-side agent, the buyer's AdCP-compliant buy-side agent can still negotiate with them. The standard creates interoperability. The marketplace provides a starting point for buyers and publishers who want a neutral, governed venue for those negotiations.