Publishers sell inventory through AdCP by running a sales agent: a server that answers buyer agents in the format the Ad Context Protocol defines. The agent declares who is authorised to sell, describes products in response to briefs, accepts or holds buys, and reports delivery. The sales team decides what the agent may offer and signs off the commitments that need a person.

TL;DR: AdCP, published and governed by AgenticAdvertising.org and launched on 15 October 2025, gives a sales agent a set list of required tasks, from capability discovery to delivery reporting. A publisher needs two declaration files on its domain, an agent that speaks MCP or A2A, and a product catalogue the agent can describe accurately. Its "submitted" status lets a buy wait for insertion order signing or human review, so judgement stays with people.

The buyer's view of the same protocol is in How the AdCP Protocol Works and Why It Matters for Buyers.

What does a publisher need before it can answer an AdCP request?

A publisher needs three things before a buyer agent will trust its answers. According to AdCP's seller integration guide, the first is an adagents.json file on each publisher domain that lists its properties and the agents authorised to sell them. The second is a brand.json file for the organisation operating the sales agent, naming the properties it represents and where buyers can find its signing keys.

The guide calls the pair a bilateral verification chain: the operator claims the property and the publisher confirms it. What Is adagents.json and How Do Publishers Authorise Seller Agents Under AdCP? covers the file field by field.

The third requirement is the agent itself. AdCP's required tasks reference says a sales agent must support at least one transport, MCP or A2A, and must answer get_adcp_capabilities, the first call a buyer makes to learn what the agent supports. Version 3.2 is the current stable line on the AdCP GitHub releases page, with 3.3 in beta.

Sell-side teams can rehearse before a real buyer arrives. As a worked example, Alkimi is neutral on standards and can work with agents built on AdCP or AAMP; its Gym lets a sell-side team build its own agent, set the rules it works to and spar it against counterparty buying agents before any real money moves.

Which AdCP tasks does a sales agent have to handle?

AdCP's 3.2 documentation lists seven tasks a Media Buy sales agent must implement. The required set, from the required tasks reference, is:

get_adcp_capabilities: tells the buyer what the agent supports.
get_products: inventory discovery against a brief or filters.
create_media_buy: campaign creation and order confirmation.
update_media_buy: changes to budget and targeting, plus pause and cancel.
get_media_buys: the current operational state of each buy.
get_media_buy_delivery: delivery metrics at package level.
provide_performance_feedback: accepts the buyer's optimisation signals.

sync_creatives becomes required when the agent hosts a creative library, and log_event once event sources are configured.

Version 3.2 also adds split tasks for new integrations: the get_products reference points new builds to list_products, request_proposals, refine_proposals and decline_proposals, and the create_media_buy reference to buy_products and accept_proposal. Both older tasks stay supported throughout 3.x, so a sales agent should expect buyers using either set.

How should a sales agent answer a buyer's brief?

A sales agent answers a brief by returning structured products, each a buyable unit with formats, pricing options and a delivery type. Every get_products request carries a buying_mode: "brief", where the publisher curates products against a natural-language brief; "wholesale", a raw product feed for buyer-directed targeting; or "refine", which iterates on an earlier response through a list of change requests.

Product detail decides whether inventory gets found: the seller integration guide says the richer the product metadata, the better buyer agents can match inventory to campaign requirements.

A sales agent does not have to say yes. The get_products documentation shows a seller declining a brief with a rejected status and a reason, and it allows brief and refine requests to return a submitted response when curation needs human review the seller cannot finish within the buyer's time budget.

The Weather Company's first sales agent, built on the open framework developed through AdCP, offered a small set of top-performing formats and audience segments to approved partners only, AdExchanger reported. "We didn't try to boil the ocean on day one," said Dave Olesnevich, VP of weather data and advertising products at The Weather Company.

How does a publisher accept a buy and keep a person in the loop?

A publisher accepts a buy through create_media_buy (or accept_proposal and buy_products in 3.2), and can answer at once or later. The seller integration guide says the buy follows the publisher's normal workflow, whether instant activation, internal review or an approval queue.

The create_media_buy reference sets out when to wait. A seller must return a submitted response when a guaranteed product is involved and the seller declares that it requires insertion order approval, or when the request triggers a governance review that cannot finish synchronously, such as manual brand-safety review for a regulated vertical. The buyer then collects the result by polling or webhook, and the response can carry a message such as "Awaiting IO signature from sales team".

The same page warns against holding everything: the choice is made per call, and sellers that return submitted for every buy fail parts of the compliance testing. Buyer-side checks that a seller calls through check_governance are covered in How Does AdCP Governance Check Budgets, Brand Safety and Human Approval Before an Agent Buys?

At The Weather Company, a person validates the availability and pricing its agent gives when a buy-side request comes in, according to the same AdExchanger report.

What does a sales agent report once a buy is live?

Once a buy is live, AdCP requires every Media Buy sales agent to implement get_media_buy_delivery and to include reporting_capabilities on every product, so buyer agents can pull impressions, clicks, spend and conversions without logging into each dashboard.

Status has to be stored, not calculated: the guide says date arithmetic cannot produce paused, cancelled or rejected states, so status should change only through protocol events.

AdCP does not replace the publisher's ad server. The guide's own comparison says AdCP sends campaign instructions while the ad server handles delivery, and OpenRTB continues to handle impression-level auctions.

What should stay with the sales team?

The sales team should keep the decisions that set value and carry risk, and hand the agent the request handling people do not enjoy. Earned autonomy, a five-step ladder an agent climbs only as it proves itself, draws that line:

Observe: the agent logs incoming briefs, so the team sees what buyer agents ask for.
Recommend: the agent suggests which products fit a brief, and a person chooses.
Draft: the agent assembles proposals for a person to review before they go out.
Human-approved action: guaranteed buys, exclusive packages and anything needing insertion order approval are held as submitted until a person signs.
Bounded automatic action: non-guaranteed products within the floors, formats and buyer lists the team has written down clear on their own.

The written-down part is the sell-side mandate: inventory tiers, floors, the deal types the agent may complete and the thresholds that trigger escalation. What a Sell-Side Agent Mandate Should Contain sets it out.

The first job for many sales agents is the long tail. "There are countless opportunities that never get executed because they're too small or customized," Patrick McCann, SVP of research at Raptive, told AdExchanger. At AdCP's launch, Scope3's Anne Coghlan told AdExchanger that "there is always a human in the loop", with large campaigns not booked without a person's approval.

Does a publisher have to build its own sales agent?

A publisher does not have to build from scratch. Prebid took over AdCP's sell-side agent code in January 2026 and made the Prebid Sales Agent available to all publishers on GitHub, AdExchanger reported.

The Prebid Sales Agent README describes an open-source sales agent that exposes inventory over MCP and A2A and integrates with ad servers such as Google Ad Manager. It labels the software alpha and calls it "one of several AdCP sales-agent implementations". Garrett McGrath, chairman of the Prebid board, told AdExchanger it is a "reference implementation" that publishers can adapt.

Other publishers use agents supplied by their technology partners. Digiday reported that smaller publishers are using partner-supplied agents for tasks such as RFP interpretation, campaign planning and optimisation.

Where does a neutral marketplace fit for a publisher?

A publisher's sales agent will meet buyer agents built on IAB Tech Lab's AAMP, the Agentic Advertising Management Protocols, as well as on AdCP. Authorisation, product description, approval and reporting matter whichever standard the buyer uses.

Alkimi is neutral on standards and works across three products. Concourse benchmarks any buying agent without asking which standard it uses; the Gym trains and spars any agent regardless of protocol; and the Marketplace is a neutral venue, usable with or without a DSP, where people keep approval rights at deal level and agreed terms are written to a DealSheet that both parties hold and either can retrieve independently. Agents take the routine requests; people approve the deals that matter.

Frequently asked questions

How do publishers sell inventory through AdCP?

Publishers run a sales agent that answers buyer agents through AdCP tasks such as get_products, create_media_buy and get_media_buy_delivery. They also publish adagents.json and brand.json so buyers can check that the agent is authorised.

Which AdCP tasks must a sales agent support?

The 3.2 required list is get_adcp_capabilities, get_products, create_media_buy, update_media_buy, get_media_buys, get_media_buy_delivery and provide_performance_feedback. Creative and event tasks become required only when the agent offers those features.

Can a sales agent turn down a buyer's brief?

Yes, a get_products response can carry a rejected status with a reason. A buy can also be held as submitted while a person reviews it.

Does AdCP replace the publisher's ad server?

No, the AdCP seller integration guide says AdCP sends campaign instructions while the ad server handles delivery. OpenRTB continues to handle impression-level auctions.

Should a sales agent approve guaranteed deals on its own?

AdCP expects a seller that requires insertion order approval for guaranteed products to return a submitted response and wait for that approval. Most sales teams will want a named person to sign those deals until the agent has earned more autonomy.