AAMP, AdCP, A2A and MCP are often listed together as "the agentic advertising protocols", but they work at two different layers. AAMP, from IAB Tech Lab, and AdCP, from AgenticAdvertising.org, are advertising-specific: they define what buyer and seller agents say to each other about products, proposals, deals and delivery. A2A and MCP are general-purpose: they define how an AI agent reaches another agent or a tool, in any industry. An agent that supports A2A or MCP can hold a conversation. Only an advertising protocol tells it what a deal is.

TL;DR. AAMP, the Agentic Advertising Management Protocols, is IAB Tech Lab's open-source framework for agentic advertising, built to extend existing standards such as OpenRTB and the Deals API. AdCP, the Ad Context Protocol, is a separate advertising protocol published by AgenticAdvertising.org that defines named tasks across a campaign and runs over MCP or A2A. A2A is an agent-to-agent communication protocol originally announced by Google in 2025, and MCP, the Model Context Protocol, was introduced by Anthropic in 2024 to connect AI assistants to tools and data. General-purpose protocols carry the messages; advertising protocols define what those messages mean in a media buy. None of the four, on its own, gives buyer and seller one shared record of the terms they agreed.

What is the difference between a transport protocol and an advertising protocol?

A transport protocol defines how one piece of software finds another, sends it a request and receives a response. An advertising protocol defines what that request contains: the product on offer, the price, the flight dates, the deal type, the delivery report. The two layers answer different questions, in the same way that the protocol carrying a web page does not know or care what the page says.

The two are easy to confuse in vendor conversations. "Our agent supports A2A" answers the question "can this agent talk to other agents?". It does not answer "can this agent buy a programmatic guaranteed deal from my seller agent and report delivery against it?". The second question needs an advertising protocol, and both sides need to speak the same one.

What is AAMP and what does it standardise?

AAMP is IAB Tech Lab's umbrella for all of its agentic advertising work, announced in early 2026. It is open source and made up of separately versioned components rather than one specification. IAB Tech Lab frames the work as "agentifying" existing standards: AAMP adds what agents need to use OpenRTB, deal IDs and the Deals API, rather than asking the market to start again.

Agentic-direct is the core communication framework and orchestration layer for agent interaction. Reference buyer-agent and seller-agent implementations show demand-side and supply-side logic. OpenProposal standardises how publishers define products and packages and represent them in RFP responses. A registry example demonstrates agent discovery and registration. The Agentic RTB Framework supports agent services that run inside a host platform, and agentic-audiences addresses interoperability between agents working with audiences. According to IAB Tech Lab, AAMP's support for the Deals API covers programmatic guaranteed, preferred deals, private marketplaces, the open marketplace and linear GRPs.

IAB Tech Lab also runs an Agent Registry in its Tools Portal, where companies list the MCP and A2A agents they bring to market. That is not a statement about which transport each AAMP component specifies; the component documentation on GitHub is the place to check that.

What is AdCP and how does it use MCP and A2A?

AdCP, the Ad Context Protocol, is an open protocol published and governed by AgenticAdvertising.org. It is not an IAB Tech Lab standard. AdCP defines a set of tasks agents call at each stage of a campaign: get_products to discover inventory, create_media_buy to execute a buy, check_governance to validate budget, brand safety and targeting before execution, and get_media_buy_delivery to report. Version 3.2 is the current general release, according to the AdCP documentation. In 3.2, get_products and create_media_buy remain supported, but new integrations use list_products or request_proposals for discovery and buy_products or accept_proposal to buy.

AdCP is explicit about transport. The same tasks and schemas run over MCP, used when an AI assistant calls tools, and over A2A, used when agents collaborate directly.

What is A2A?

A2A is an agent-to-agent communication protocol originally announced by Google in 2025. It is general-purpose: it gives agents built by different vendors a common way to discover what another agent can do, exchange messages and coordinate on a task. Nothing in A2A is specific to advertising.

In a media transaction, A2A fits the peer relationship between a buyer agent and a seller agent, where each side acts for a different principal and neither is simply a tool of the other. What the two agents negotiate about, and in what format, comes from the advertising protocol running on top.

What is MCP?

MCP, the Model Context Protocol, was introduced by Anthropic in 2024 as an open protocol for connecting AI assistants to tools and data sources. The relationship it describes is a client calling a capability: an assistant asks a server to run a function or return data, and the server responds.

In advertising, that pattern suits cases where one side exposes capabilities for the other to use, such as a seller making inventory discovery available to any assistant that connects. MCP is also general-purpose, so the meaning of "inventory" in that exchange still has to come from an advertising protocol.

How do the four protocols fit together in a single media buy?

Take a hypothetical buyer agent working on an agency brief. It finds seller agents through a registry, reads each publisher's products and packages, negotiates terms within its mandate, executes a deal and later collects delivery data.

At each step there are two questions. The advertising question is what the message contains and what it commits the parties to: in AAMP terms, an OpenProposal response or a Deals API deal type; in AdCP terms, a task such as get_products or create_media_buy. The transport question is how the message travels: over A2A between peer agents, over MCP from an assistant to a tool, or over whatever the component specifies. A buyer evaluating vendors needs answers to both.

Which protocol questions should a buyer or publisher ask a vendor?

Five questions separate a working integration from a slide. Which advertising protocol does the agent speak, AAMP, AdCP or both, and at which component or release version? Which deal types does it support? Is the agent listed in the IAB Tech Lab Agent Registry? Which transport does it use to reach counterparties? And what record of the agreed terms exists after the deal, and does the counterparty hold the same record?

The last question sits outside all four protocols. Settlement and disputes depend on both parties holding the same version of what was agreed. Alkimi, an agentic advertising marketplace, works within IAB Tech Lab's AAMP framework and has its agent listed in the Agent Registry; buy-side and sell-side agents agree terms on a shared DealSheet that both parties hold, with humans keeping approval rights at the deal level.

Frequently asked questions

Is A2A an advertising protocol?

No. A2A is a general-purpose agent-to-agent communication protocol, originally announced by Google in 2025. It carries messages between agents in any industry; advertising meaning comes from a protocol such as AAMP or AdCP.

Is MCP an advertising protocol?

No. MCP, the Model Context Protocol, was introduced by Anthropic in 2024 to connect AI assistants to tools and data. It defines how an assistant calls a capability, not what an advertising deal contains.

Does AdCP run over MCP or A2A?

Both. According to the AdCP documentation, the same tasks and schemas run over MCP, when an AI assistant calls tools, and over A2A, when agents collaborate directly.

What is the difference between AAMP and AdCP?

AAMP is IAB Tech Lab's framework of separately versioned components that extend existing standards such as OpenRTB and the Deals API for agents. AdCP is a separate protocol from AgenticAdvertising.org that defines named tasks across a campaign. Whether they converge, coexist or compete is still open.

AAMP, AdCP, A2A and MCP: Which Protocol Does What in Agentic Advertising?