Three acronyms, one conversation, and most people using them are not talking about the same layer of the stack. That confusion is doing real damage to how buyers and publishers think about what "going agentic" actually requires, so here's what each one is, in one paragraph each, with no hedging.

AdCP

The Ad Context Protocol. A shared format for buying and selling agents to exchange structured information: what inventory exists, what it costs, what targeting is available, what terms are on offer. Think of it as the vocabulary two agents use to describe a media deal to each other. It covers discovery and proposal exchange. It does not cover who approved the deal, where it's recorded, or what happens if delivery doesn't match what was promised.

AAMP

The Agentic Advertising Marketplace Protocol, generally used to describe a model where agents transact directly through a shared marketplace layer rather than a point-to-point connection between every buyer and every publisher. It's a different problem to AdCP, not a competing answer to the same one. AdCP is about how two agents talk. AAMP-style thinking is about where that conversation happens, and whether it happens through a shared venue or a direct line.

A2A

Agent-to-agent, a general term for the broader category of protocols that let autonomous software systems communicate directly with each other, not specific to advertising. AdCP is one implementation of an A2A pattern, scoped to media buying. A2A as a term shows up across industries wherever people are building standards for agents to talk without a human relaying messages between them.

Why the overlap confuses people

Each of these answers a question about communication: what gets said, where it gets said, and in what general pattern. None of them answers the question that actually determines whether an agentic deal is safe to run: who is accountable for it, is there a record both sides trust, did a human see it before it went live. That's a separate layer, and it's the layer most of this terminology gets mistaken for covering.

Where this leaves a buyer trying to make a decision

Don't pick a side in a standards war that hasn't been decided and may never fully settle, the way RTB and header bidding both had their moment without either becoming the permanently final word. Pick infrastructure that integrates with whichever protocol your counterparties are using today, and that puts the governance layer, the deal record, the approval step, the audit trail, above the protocol rather than tied to one of them. That's a standard-neutral position, not a hedge. It's the only position that survives whichever acronym wins.