AdCP / Advertising Context Protocol.

Fast read

What it is

An open agentic advertising protocol that defines domain-specific tasks and schemas for advertising agents.

What it does

Helps agents discover inventory, set up accounts, buy media, manage creative, activate signals, apply governance, and report results through standardized calls.

What it is not

Not a media exchange, identity graph, DSP, SSP, clean room, or replacement for OpenRTB.

Why it matters

Agentic workflows need repeatable, machine-readable actions. Without a shared protocol, every agent has to learn every platform separately.

Current state

AdCP 3.1 remains the general-availability line and the production recommendation; the latest stable tag is v3.1.23 (GitHub, September 14, 2026), whose #7406 backports the <code>required_tools</code> OR-gate fixes to 3.1.x: <code>canonical_format_validate_input</code> drops <code>comply_test_controller</code> (filed as #7404; #7405 on main), and four storyboards drop <code>get_adcp_capabilities</code> (the applicable subset of #6774). #7451 corrects the v3.1.22 release record to name the request-aware cache partitioning that shipped without changelog coverage. The 3.2 line is at v3.2.0-rc.3 (September 14, 2026), which the official versions page marks development and staging only — pin "3.2-rc.3" solely against peers that advertise it, and keep production on wire pin "3.1". The versions page still says no SDK embeds rc.3; that lapsed on September 15, 2026, when @adcp/sdk 14.0.0-rc.37 and Python adcp 8.0.0b15 both shipped declaring ADCP_VERSION 3.2.0-rc.3. Only Go adcp/v3.2.1 remains on rc.1. The docs are explicit that patch components are never sent. 3.1 is additive over 3.0 and supported patches do not change stable wire surfaces, so a 3.0 integration keeps working with no code change; v3.1.22 did change the explicitly experimental TMP contract, under the emergency exception to the normal notice process. v3.1.3 was withdrawn days after shipping (see the version-watch section below). Validate implementation details against current official docs.

Best next step

Understand the domains, then decide which workflow your company should expose or consume first.

• Fragmented workflows

  Media buying, creative, data activation, accounts, and reporting still live across disconnected systems and dashboards.

• Agents need actions, not screens

  An agent cannot scale by clicking through every platform UI. It needs task-level interfaces.

• Common schemas reduce ambiguity

  Natural-language briefs need to resolve into structured, auditable requests.

• Human oversight needs architecture

  Agentic buying requires approvals, limits, audit logs, and accountability built into the flow.

• Platform participation needs standards

  Publishers, data providers, creative systems, and ad platforms need a shared way to expose what agents are allowed to do.

Not protocol work — bug reports and a feature request against the AAO platform

• Shipped as filed, one of them only in part — the member profile edit page threw parsed is not defined on load, a one-line scoping error (#4257), and photo uploads on the same page reverted silently on save, from two compounding causes: the upload handler wrote a base64 data URL the brand-identity endpoint rejects, and the save never sent the photo field (#4260). Both were fixed in PR #4352, merged May 10, 2026, which references neither issue; its description credits my in-app escalations of the same two defects, and both issues were closed on May 12 with a comment pointing to it. Badge links of the form /registry/agents/{encoded-url} returned Cannot GET (#5485) until PR #5492, a five-issue batch merged June 12, 2026, served that path as a public agent profile page. A “0 / 0 Community seats” row on a Professional plan, which the filing itself called display-only (#5494), was hidden on plans without Community seats by a small conditional (PR #5586, merged June 18, 2026). A copy button for replies in AAO’s Addie assistant shipped (#4266 → PR #4269) without the plain-text/markdown toggle the request also asked for, which the bot triage declined and the PR left out of scope.
• Wrong or partial diagnoses, and one wrong report — the dashboard’s Test view listed media-buy storyboards for a signals-only agent; filed as missing capability filtering, but the filter already existed, and a fallback to the full catalog, taken when the platform’s capability probe of my agent failed for a reason the record does not give, bypassed it. The fix drops the fallback and shows the probe error, with a pointer to what get_adcp_capabilities must return, rather than the filtered list the filing expected (#4254 → PR #4369). The member directory showed “Tools: 0” for an agent with eight tools; filed as a stale comply cache, a theory the fixing PR calls incorrect: the public discovery endpoint probed the agent live and left the tool list out of its response (#4256 → PR #4261). The organization page offered “Register an agent” to an org that had one; the filing guessed the page was not querying the registry or was filtering on a stale comply cache, and the health service in fact returned a hard-coded agent count of zero (#4255 → PR #4258). Listing the org’s agents on that page, the filing’s first expected behaviour and its whole suggested fix, was left out of scope by the bot triage and the PR. Addie kept reporting GitHub as unconnected for a turn after OAuth completed; the bot triage and the fixing PR found the token lookup already ran live on every tool call, which rules out the filing’s caching guesses, and put the lag down to propagation delay in the upstream WorkOS API, which none of the filing’s three guesses named. The fix is a single 1.5-second retry that absorbs that window, a note in the not-connected reply that the connection may still be propagating, and a prompt rule that stops Addie offering the Connect link again right after the user says it is connected; none of it is a change to connection state (#4348 → PR #4349). And one report was wrong. A community profile photo picker, on a different page from #4260, reported as broken, was the reference-photo input for AI portrait generation: the filing’s own steps name it (“Upload a reference photo”), and the bot triage found its hint reads “Used as reference only, not stored” and that the avatar changes only after Generate and Approve. That triage put a choice between a direct upload path and clearer labels to the maintainer, and the merged fix built the upload path (#4658 → PR #5157, merged May 29, 2026).
• Registry & docs reliability — registry UI rendering empty product/format sections for anonymous viewers despite working public endpoints (#6229, fixed and closed; my own duplicate of it, #6230, filed 57 seconds later, drew a bot triage the same day that surfaced a third break in publisher discovery; I carried that finding across when I closed #6230 as a duplicate on August 6, 2026, which GitHub records as not planned, and it was fixed in the same change) and the dashboard's aao-verified doc links returning 404 (#6231, fixed and closed). The registry card's "Publishers & properties" panel surfacing a raw JSON-parse exception instead of the actual authorization-list cause (#7333) is fixed too — PR #7362 now indexes publisher authorization data, guards invalid JSON responses, and renders clean 404/error states.

Contribution statuses validated September 16, 2026 against the public AdCP repository; open proposals are point-in-time and may merge, change, or close. Maintainer-authored work is credited as review influence, not authorship.

• Media Buy

  Inventory discovery, campaign creation, delivery reporting.

  get_products · create_media_buy · get_media_buy_delivery

• Creative

  Creative format discovery, building, preview, distribution.

  build_creative · preview_creative · list_creative_formats

• Signals

  Audience and contextual data discovery and activation.

  get_signals · activate_signal

• Accounts

  Commercial identity, billing, and usage reporting.

  list_accounts · sync_accounts · report_usage

• Governance

  Brand suitability, approval, policy, audit, content standards.

  create_content_standards · calibrate_content

• Brand

  Machine-readable brand identity and authorized agents via brand.json.

  brand.json discovery

• Sponsored Intelligence

  Conversational brand experiences on AI platforms.

  Experimental surface in AdCP 3.0

• Curation

  Media inventory curation.

  Listed "coming soon" — not a current domain

• Discover

  What signals exist and what do they mean?

• Inspect

  Where did the signal come from, how fresh is it, and what policy applies?

• Activate

  Where can the signal run: seller, platform, identity path, contextual path, or measurement layer?

• Monitor

  What is the activation status and what outcome did it improve?

An agent discovers signals with a natural-language brief, then activates the chosen signal to a destination — a single get_signals call rather than a taxonomy lookup:

{
  "tool": "get_signals",
  "arguments": {
    "brief": "in-market for premium CTV, US households, privacy-safe",
    "deliver_to": { "platform": "dsp", "account": "acct_123" },
    "max_results": 10
  }
}

One open question now sits under this layer. The vectors agents exchange today are text-family embeddings — they encode the words that describe an audience or a brief, and text models famously lose numbers, geography, and time. A second family, spatiotemporal embeddings, encodes the place and hour themselves. A text space and a place-time space do not share a geometry: similarity across the two is undefined until someone defines it — a signals-standards question, exactly the kind of definition a signals working group exists to produce, not an integration ticket.

• Start with one workflow, not every workflow.
• Expose the safest useful task first.
• Design governance before spend movement.
• Treat signals as governed objects, not just segment IDs.
• Build audit and status from day one.
• Connect protocol work to business outcomes, not demos.

• Core AdTech Standards
• Privacy & Consent Standards
• Measurement & Media Quality
• IAB Agentic Standards
• Research & Measurement Science