Last updated: 14 October 2026

A protocol cannot settle a media deal on its own, because settlement is not a message format. A protocol defines how two parties' software discovers inventory, exchanges proposals, executes buys and reports delivery. Settling the deal needs something a protocol does not supply: one record of the agreed terms that both parties accept, a rule for what happens when delivery and terms diverge, and an accountable party to apply that rule. Those sit in a marketplace or in the contract between buyer and seller.

TL;DR. AAMP, from IAB Tech Lab, and AdCP, from AgenticAdvertising.org, standardise how agents communicate and transact; neither is designed to be the commercial venue where disputes are resolved. The AdCP documentation states that payments, legal agreements, settlement, disputes, credits and makegoods remain account or platform integrations unless a specific AdCP contract covers them. Each party logging its own copy of a protocol exchange produces two records, and two records diverge. A marketplace adds the parts settlement depends on: admission rules, a shared record of terms, a process for discrepancies and human approval points. The protocol and the marketplace are layers, not rivals.

What does an advertising protocol standardise?

An advertising protocol standardises the shape of the conversation: which messages exist, what fields they carry and how they travel. OpenRTB did this for the auction, so any DSP could bid into any SSP. It did not decide how the resulting invoices were reconciled.

The agentic protocols follow the same pattern at a larger scale. AAMP, IAB Tech Lab's Agentic Advertising Management Protocols, is a framework of separately versioned components: agentic-direct for agent communication and orchestration, reference buyer and seller agents, OpenProposal for how publishers describe products and RFP responses, a registry example for agent discovery, the Agentic RTB Framework and agentic-audiences. AdCP, the Ad Context Protocol, defines tasks from get_products for discovery to create_media_buy for execution and get_media_buy_delivery for reporting, running over MCP or A2A. Both make it possible for agents built by different companies to transact without a custom integration. That is interoperability, which is necessary for settlement but not the same thing.

What does settling a media deal actually require?

Settling a media deal means both parties agreeing what was delivered against what was bought, and what money moves as a result. That requires four things: a record of the agreed terms that neither side can later dispute the content of; delivery evidence measured on the basis those terms specify; rules for discrepancies, such as tolerances, makegoods and credits; and a named party, human or organisational, that applies those rules.

A hypothetical example shows where a protocol stops. A buyer agent and a seller agent agree a £40,000 programmatic guaranteed deal for 2,000,000 impressions over four weeks. Every message is exchanged correctly. At the end of the flight the seller's ad server counts 2,000,000 impressions served, while the buyer's verification vendor counts 1,700,000 that met the viewability standard. The protocol carried every message, but it cannot say which count governs the invoice. That answer depends on what the two parties agreed the billing basis was, and on whether both still hold the same version of that agreement.

Why can't the protocol exchange itself serve as the deal record?

Each party to a protocol exchange keeps its own log of the messages it sent and received. Two logs of the same conversation drift apart for ordinary reasons: a retried request, a counter-offer amended after a timeout, a term confirmed in one system but not written back to the other, different time zones in reporting. Request signing and audit logs, both described in the AdCP documentation, help each party prove what it sent. They do not by themselves produce one agreed statement of the commercial terms, held identically by both sides.

The scale of that drift is the core argument for a shared record. In the Agree. Transact. Verify. simulation of 90,202 deals, buyer and seller records kept separately disagreed in 95.3% of cases, against 0.19% when both parties worked from one shared record. A protocol carries the messages that create the agreement. The shared record is where the agreement lives.

What does a marketplace add that a standard cannot?

A standards body publishes specifications and, by design, does not run transactions. A marketplace, meaning a venue where buyers and sellers transact under common rules, supplies the operational parts a specification leaves open:

admission rules: which agents may participate, and checks that each acts for a real principal;
a shared record: terms written once, at the moment of agreement, and held by both parties;
discrepancy rules: the measurement basis and tolerances agreed in advance, so a gap has a pre-agreed resolution;
human approval points: commitments above a threshold held until a person signs off;
accountability: a known party that maintains the record and the rules.

A bilateral contract can supply some of these for a single relationship. A marketplace supplies them consistently across many counterparties, which matters when agents can open far more negotiations than a sales team could.

Do marketplaces compete with protocols like AAMP and AdCP?

No. A marketplace can sit on top of a protocol in the way an exchange sits on top of OpenRTB. The protocol lets agents from different companies reach each other and speak a common language; the marketplace decides the commercial rules under which they transact and keeps the record. A buyer choosing between venues should ask which protocols each supports and at which version, but should judge the venue on settlement: who holds the record, how discrepancies are resolved and where humans approve.

What should buyers and publishers ask before agents settle deals?

Before letting agents agree deals that will need to settle, both sides should be able to answer six questions:

Where is the record of agreed terms held, and can each party retrieve it independently?
Is the record written at the moment of agreement, or reconstructed afterwards from logs?
Which measurement source and basis govern billing?
What tolerance, makegood or credit applies if delivery falls short?
Which commitments require human approval, and by whom?
Which protocol and version are the agents using, and which deal types does it cover?

Alkimi, which published the Agree. Transact. Verify. simulation, answers the first two questions as a neutral agentic advertising marketplace working within IAB Tech Lab's AAMP framework: each DealSheet is written at agreement, timestamped and held by both parties, with humans keeping approval rights at the deal level.

Frequently asked questions

What is the difference between a protocol and a marketplace in advertising?

A protocol defines how software exchanges messages and executes tasks. A marketplace is a venue where buyers and sellers transact under common rules, including how agreed terms are recorded and how discrepancies are resolved.

Does AdCP handle settlement and disputes?

Not by default. The AdCP documentation states that payments, legal agreements, settlement, disputes, credits and makegoods remain account or platform integrations unless a specific AdCP contract is present.

Does AAMP provide a shared deal record?

AAMP standardises agent communication, publisher product descriptions, agent discovery and connections to existing deal types. It does not by itself give buyer and seller a single shared record of agreed commercial terms.

Why is a shared deal record better than each side keeping its own logs?

Separate logs drift apart through retries, amendments and system differences. One record written at agreement and held by both parties gives a dispute a single reference point.

Can a bilateral contract replace a marketplace for settlement?

For a single relationship, a contract can define the record, measurement basis and discrepancy rules. A marketplace applies the same rules across many counterparties, which matters as agents open more negotiations.

Protocol vs Marketplace: Why Can't a Standard Alone Settle a Media Deal?