AdCP — Creative Specification

AdCP 3.0 Proposal - This specification is under development for AdCP 3.0. Feedback welcome via GitHub Discussions.

Canonical formats in 3.1: this page describes the v1 specification model. For the canonical-formats model (inline format_options on products, validate_input primitive), see canonical-formats and the migration guide.

Status: Request for Comments Last Updated: March 2026 The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL” in this document are to be interpreted as described in RFC 2119.

Abstract

The Creative Protocol defines a standard interface for creative format discovery, manifest validation, creative generation, and preview rendering. This protocol enables AI agents to discover format specifications, build compliant creative assets, and generate previews across advertising platforms.

Protocol overview

The Creative Protocol provides:

Format discovery with full technical specifications
Manifest validation against format requirements
AI-powered creative generation and transformation
Preview rendering for creative verification
Universal macros for cross-platform tracking

Transport requirements

Creative agents MUST support at least one of the following transports:

Transport	Protocol	Description
MCP	Model Context Protocol	Tool-based interaction via JSON-RPC
A2A	Agent-to-Agent	Message-based interaction

Creative agents SHOULD support MCP as the preferred transport. Creative agents MUST declare Creative Protocol support via get_adcp_capabilities:

{
  "$schema": "https://adcontextprotocol.org/schemas/v3/protocol/get-adcp-capabilities-response.json",
  "status": "completed",
  "adcp": {
    "major_versions": [2],
    "idempotency": { "supported": true, "replay_ttl_seconds": 86400 }
  },
  "supported_protocols": ["creative"],
  "creative": {
    "has_creative_library": true,
    "supports_generation": false,
    "supports_transformation": true,
    "supports_compliance": false
  }
}

The creative capabilities tell the buyer which interaction models this agent supports. See Interaction models below.

Core concepts

Creative agents

A creative agent is any agent that implements the Creative Protocol. This includes standalone services (ad servers, creative management platforms, generative tools) and sales agents that declare "creative" in supported_protocols. A creative agent:

Defines and documents formats it owns
Validates manifests against format requirements
Generates previews showing how creatives will render
Optionally generates or transforms creatives from natural language briefs

Sales agents that implement both the Media Buy Protocol and the Creative Protocol serve both roles from a single endpoint. See Creative capabilities on sales agents.

Interaction models

Creative agents serve different roles depending on their capabilities. Buyers use get_adcp_capabilities to determine which interaction model applies:

Model	Description	Capabilities	Examples
Transformation agent	Resizes or adapts existing manifests to new formats	`supports_transformation: true`	Format conversion services
Generative agent	Creates manifests from natural language briefs	`supports_generation: true`	AI creative platforms
Creative ad server	Hosts a creative library, generates ad-serving tags	`has_creative_library: true`	Flashtalking, CM360, Celtra

These models compose — an agent can support multiple. A creative ad server with supports_generation: true and has_creative_library: true can both generate creatives from briefs and retrieve existing ones from its library. The supports_compliance flag is orthogonal — any interaction model can support compliance requirements in briefs. Buyer workflow by model:

Transformation: list_creative_formats → build_creative (with creative_manifest + target_format_id)
Generation: list_creative_formats → build_creative (with message + target_format_id)
Library retrieval: list_creatives → build_creative (with creative_id + target_format_id)

Agents that host a creative library should also implement the accounts protocol so buyers can establish access before querying. Sales agents that already implement accounts for media buys do not need to do anything additional. A transformation or generation agent that charges for its services implements the Accounts Protocol, exposes pricing_options on list_creative_formats, and returns pricing in build_creative responses. Agents that persist creative_id on build output can also expose pricing on list_creatives. Free transformation agents remain stateless and unchanged.

Format authority

Each format has exactly one authoritative creative agent, identified by the agent_url in the format ID:

{
  "format_id": {
    "agent_url": "https://creative.adcontextprotocol.org",
    "id": "display_300x250_image"
  }
}

Creative agents MUST only return authoritative format definitions for formats they own. Creative agents MAY reference other creative agents that provide additional formats.

Formats

Formats define how assets are assembled and rendered. A format specifies:

Media family (display, video, audio, dooh)
Required and optional asset types
Technical constraints (dimensions, duration, file size, codecs)
Rendering behavior and interaction expectations

Assets

Assets are the building blocks of creatives. Asset types include:

image: Static images (JPEG, PNG, WebP, GIF)
video: Video files (MP4, WebM, MOV) or VAST tags
audio: Audio files (MP3, M4A) or DAAST tags
text: Headlines, descriptions, CTAs
html: HTML5 creatives or third-party tags
javascript: JavaScript tags
url: Tracking pixels, clickthrough URLs

Manifests

Manifests pair format specifications with actual asset content. A manifest provides:

Format reference (agent_url + id)
Asset values keyed by asset_id from the format
Tracking URLs and macros

Creative agents MUST validate manifests against format requirements before accepting them.

Universal macros

AdCP defines universal macros for cross-platform tracking. Creative agents MUST support these macros in tracking URLs:

{TIMESTAMP}: Unix timestamp
{CACHEBUSTER}: Random cache-busting value
{CLICK_URL}: Click tracking URL
{REDIRECT_URL}: Final destination URL

Sales agents MUST translate universal macros to their ad server’s native syntax.

Creative Status Lifecycle

Schema: enums/creative-status.json Creatives in a library progress through a defined set of states. Most transitions are seller-initiated (processing, review, approval/rejection). suspended is a recoverable offline state for approved creatives whose dependencies become unavailable, such as an expired published-post authorization. archived is reached either by buyer cleanup or by seller-side lifecycle policy on creatives without active assignments — see the rules below.

sync_creatives ──▶ processing ──▶ pending_review ──▶ approved
                       │                 │              │
                       │                 │              ├──▶ suspended ──▶ approved
                       │                 │              │        │
                       │                 │              │        └──▶ rejected
                       │                 │              ├──▶ pending_review
                       │                 │              ├──▶ rejected
                       │                 │              └──▶ archived
                       │                 │
                       └──────▶ rejected ◀──────────────┘
                                  │
                                  └── buyer fixes + resubmits ──▶ processing

archived ── buyer unarchives ──▶ approved (or pending_review when re-review is required)

Rules:

processing → pending_review: automatic when ingestion and transcoding succeed
processing → rejected: automatic when processing fails (corrupt file, unsupported codec, constraint violation)
pending_review → approved: seller approves after content policy review
pending_review → rejected: seller rejects with rejection_reason
approved → suspended: seller detects a recoverable dependency/authorization loss, such as identity_authorization_revoked, identity_authorization_expired, or source_private for a published_post reference. Sellers MUST surface a corresponding impairment on affected active buys.
suspended → approved: seller observes that the dependency is restored and any required re-review passes.
suspended → rejected: seller determines that a previously recoverable dependency/authorization loss cannot be restored for this creative, or that replacement/resubmission is required. Example: a revoked identity/post authorization for a published_post reference cannot be reauthorized. Sellers MUST keep affected active buys impaired until the creative is replaced, reassigned, or the package/buy is otherwise remediated.
approved → archived (buyer-initiated): buyer issues archive via sync_creatives
approved → archived (seller-initiated): seller archives an unassigned creative for inactivity, post-flight expiry, or storage policy. Sellers MUST NOT seller-archive a creative that has active package assignments — the approved → rejected (revocation) path with an impairment on the affected buy is the only conformant route when active serving is involved. State-change observability for seller-initiated archive follows the creative retention contract — minimally, the new status MUST be visible on the next list_creatives read.
archived → approved: buyer-initiated via sync_creatives (unarchive). Sellers MAY require re-review, transitioning to pending_review instead.
rejected → processing: buyer fixes the creative and resubmits via sync_creatives. The creative re-enters the full processing and review pipeline.
approved → pending_review: seller-initiated re-review (e.g., policy change). Sellers MUST notify subscribers via creative.status_changed (fired to each notification_configs[] subscriber whose event_types[] includes this value — see below) when a previously approved creative is pulled back for re-review.

Creative agents MUST reject operations that reference a rejected creative for delivery (e.g., assigning it to a package) with error code CREATIVE_REJECTED. Creative agents MUST also prevent delivery of suspended creatives until the dependency is restored. Creative agents MUST include status and rejection_reason (when rejected) in list_creatives responses.

Lifecycle webhooks

Seller-initiated and system-initiated transitions fire push notifications against the account’s notification_configs[] subscribers — each entry whose event_types[] includes the fired type receives an independent fire. Two event types cover the surface:

creative.status_changed — fires on every seller-initiated or system-initiated transition: pending_review → approved/rejected, approved → pending_review (re-review), approved → suspended (recoverable dependency/authorization loss), suspended → approved (recovery), suspended → rejected (terminal dependency/authorization loss), approved → rejected (post-approval revocation), approved → archived (seller-initiated). Payload: creative-status-changed-webhook.json.
creative.purged — fires when a creative is destroyed (retention sweep, takedown, legal erasure). soft purges retain a tombstone on list_creatives (with include_purged: true) for 30 days; hard purges retain no record — the webhook is the buyer’s only signal. Payload: creative-purged-webhook.json.

Buyer-initiated transitions (archive, unarchive, resubmit) do NOT fire — those are acknowledged on the sync_creatives response path. The push channel exists only for transitions the buyer did not initiate. Both events carry a categorical reason_code drawn from creative-event-reason-code.json. Buyer-side remediation per reason code is documented inline on the enum’s enumDescriptions. When a creative transitions to a state that breaks active serving (approved → suspended, approved → rejected, suspended → rejected, or seller-initiated approved → archived while assignments exist — which is non-conformant; see the transition rules above), the seller MUST also surface a corresponding impairment on every media buy referencing the creative (see Media buy health). The creative-side creative.status_changed and the buy-side impairment are paired but distinct signals; buyers correlate by creative_id. The two surfaces have different anchors: creative events fire account-level (subscriptions outlive any one buy); impairments fire per-buy. No ordering guarantee between the paired fires — buyers MUST NOT assume one arrives before the other; reconcile via the snapshot (list_creatives and get_media_buys). Sellers declare which event types they support and per-type coalescence windows via get_adcp_capabilities. Default coalescence is 5 minutes for creative.status_changed; sellers MUST NOT coalesce creative.purged. Retroactive contract: when a seller declares support for these event types, the obligation covers all creatives in the library — no grace period for pre-existing creatives. Buyers MAY pull recent webhook fires per creative via list_creatives with include_webhook_activity: true. The read surface follows the webhook_activity[] adoption checklist — 30-day retention, three-state presence semantics, idempotency_key correlation to buyer-side endpoint logs.

Pricing

Creative agents that charge for their services expose pricing through the same discover → build → report loop used by signals agents and content standards agents.

Pricing discovery surfaces

Pricing is discovered via two surfaces depending on the agent’s interaction model:

list_creatives — ad servers and library-based agents expose pricing_options[] on each creative. The buyer discovers pricing for specific creatives they want to use.
list_creative_formats — transformation and generation agents expose pricing_options[] on each format. The buyer discovers pricing for the formats the agent can produce, before any creative exists.

Both surfaces use the same pricing_options[] array of vendor-pricing-option objects. Both require account and include_pricing: true on the request. An agent MAY expose pricing on both surfaces (e.g., a creative management platform that has both a library and transformation capabilities).

Pricing flow

Account setup — rate card agreed. Determines pricing for all subsequent operations.
Discovery — list_creatives or list_creative_formats with account and include_pricing: true returns pricing_options[]. Vendors may offer multiple options (volume tiers, context-specific rates, different models per product line).
Build — build_creative with account. The agent computes the cost and returns pricing_option_id, vendor_cost, currency, and consumption in the response.
Report — report_usage with creative_id and pricing_option_id for reconciliation.

Pricing models

Creative agents reuse the vendor pricing models defined in vendor-pricing-option.json:

Model	Creative use case
`cpm`	Cost per thousand impressions served — ad server model, DCO platforms
`percent_of_media`	Percentage of media spend — agency/platform model
`flat_fee`	Fixed charge per period — licensed creative suites, subscription access
`per_unit`	Fixed price per unit of work — per format adapted, per image generated, per token, per variant rendered

Consumption details

Schema: core/creative-consumption.json The build_creative response includes a consumption object with structured details about what was consumed. Well-known fields: tokens (LLM tokens consumed), images_generated, renders (render passes), duration_seconds (processing time). Agents MAY include additional fields. The consumption object is informational — it lets the buyer verify that vendor_cost is consistent with the rate card. vendor_cost is the billing source of truth.

Accounts requirement

Creative agents that charge for their services MUST implement the Accounts Protocol. This applies to any creative agent with pricing — ad servers, generation platforms, and transformation agents that bill for usage.

Bundled mode

When a publisher uses a creative agent internally (bundled), the buyer never sees the creative agent’s pricing. The cost is absorbed into product pricing. The sales agent is the buyer in the creative agent relationship — it establishes an account, calls build_creative, and handles report_usage. The protocol surface is the same.

Tasks

The Creative Protocol defines the following tasks. See task reference pages for complete request/response schemas and examples.

list_creative_formats

Reference: list_creative_formats task Discover creative formats and their specifications. Requirements:

Creative agents MUST return full format specifications for formats they own
Creative agents MUST include agent_url identifying the authoritative agent for each format
Creative agents MUST include technical constraints (dimensions, duration, file types) in format definitions
Creative agents MAY include references to other creative agents providing additional formats
When filtering by format_ids, creative agents MUST return only the requested formats

list_transformers

Reference: list_transformers task Discover the account-scoped transformers a creative agent offers — the creative analog of media-buy products: agent-offered, selectable units of build capability (voices, models, styles) that you select with transformer_id in build_creative. Offered only by agents that declare creative.supports_transformers: true in get_adcp_capabilities. Requirements:

Creative agents that set creative.supports_transformers: true MUST implement list_transformers
Creative agents MUST resolve transformers, their enumerable option values, and pricing for the calling account — including custom values configured for that account (e.g. cloned voices)
Creative agents MUST return account-scoped option values inline on params[].options[] for each field named in expand_params, and SHOULD omit them otherwise
When include_pricing is true, creative agents that charge MUST include pricing_options (the per_unit model) on each transformer

build_creative

Reference: build_creative task Transform, generate, or retrieve creative manifests. Supports three modes:

Generation: Create a manifest from a brief or seed assets
Transformation: Adapt an existing manifest to a different format
Library retrieval: Resolve a creative_id from the agent’s library into a manifest with ad-serving assets (HTML/JavaScript/VAST tags)

Requirements:

Creative agents MUST validate input manifests against format requirements
Creative agents MUST return a valid manifest for the target format on success
Creative agents MUST return validation errors if the transformation cannot be completed
Creative agents SHOULD preserve tracking URLs and macros during transformation
Creative agents SHOULD respect quality for generative tasks ("draft" for fast iteration, "production" for final delivery) and MAY ignore it for non-generative transforms
Creative agents SHOULD honor item_limit when present, using the lesser of item_limit and the format’s max_items
Creative agents MAY use AI/LLM processing for generation tasks
When creative_id is provided, creative agents MUST resolve the creative from their library
When macro_values is provided, creative agents SHOULD substitute the specified macros in the output manifest’s assets and leave unresolved macros as {MACRO} placeholders
Creative agents MUST ignore unrecognized macro keys in macro_values — unknown macros are not an error
Creative agents SHOULD assign globally unique creative_id values; when they cannot guarantee uniqueness, concept_id is REQUIRED on build_creative requests to disambiguate
build_creative supports async responses (status: "working" with context_id polling) for generation and transformation tasks that take significant time. Library retrieval is typically synchronous.
When account is provided and the agent charges, the response MUST include pricing_option_id, vendor_cost, and currency. The consumption object SHOULD be included when relevant.
For async builds, pricing fields appear on the final completed response only, not on intermediate status responses.
When a paid creative agent receives a build_creative request without account and the agent requires an account, the agent MUST return an error.

preview_creative

Reference: preview_creative task Generate preview renderings of creative manifests. Requirements:

Creative agents MUST validate manifests before generating previews
Creative agents MUST return preview URLs or HTML for valid manifests
Creative agents MUST keep preview URLs dereferenceable until their expires_at timestamp. When expires_at is omitted, preview URLs do not expire at the protocol layer and remain valid until the agent explicitly revokes them out of band.
Creative agents SHOULD include expires_at for time-limited preview URLs
Creative agents SHOULD support batch preview for multiple creatives
Creative agents MAY support multiple output formats (URL, HTML, image)

list_creatives

Schema: creative/list-creatives-request.json / creative/list-creatives-response.json Reference: list_creatives task Browse and filter creative assets in a creative library. Implemented by any agent that hosts a creative library — ad servers, creative management platforms, and sales agents that manage creatives. Requirements:

Agents MUST return creatives accessible to the authenticated account
Agents MUST include approval status for each creative
Agents SHOULD support filtering by format, status, tags, and date range
Agents SHOULD support filtering by concept_ids and format_ids when the platform organizes creatives into concepts
Agents MAY include dynamic content variable definitions when include_variables=true
Agents MAY include a lightweight delivery snapshot when include_snapshot=true. The snapshot provides lifetime impressions and last-served date for operational use — detailed analytics belong in get_creative_delivery.
When account and include_pricing=true are provided, agents that charge MUST include pricing_options on each creative — an array of vendor-pricing-option objects. Vendors may offer multiple options per creative (volume tiers, context-specific rates, different pricing models).

Account requirements:

Creative agents that charge for their services MUST implement the Accounts Protocol. This applies to any creative agent with pricing — ad servers, generation platforms, and transformation agents that bill for usage.
Creative agents that host a library but do not charge SHOULD implement the Accounts Protocol so buyers can establish access before querying.
This is the same accounts protocol used by sales agents — there is no separate version.
Sales agents that already implement accounts for media buys do not need to do anything additional.

sync_creatives

Schema: creative/sync-creatives-request.json / creative/sync-creatives-response.json Reference: sync_creatives task Upload and synchronize creative assets in a library. Implemented by any agent that hosts a creative library — ad servers, creative management platforms, and sales agents that manage creatives. Requirements:

Agents MUST validate creatives against format specifications
Agents MUST return validation errors for non-compliant creatives
Agents MAY require approval before creatives are available for use
Agents SHOULD support dry_run for validation without applying changes
Agents MUST reject requests that combine delete_missing: true with creative_ids — delete_missing applies to the entire library, not a filtered subset
Agents that also manage media buys SHOULD support the assignments field for bulk creative-to-package mapping
Standalone creative agents that do not manage media buys SHOULD ignore the assignments field

get_creative_delivery

Reference: get_creative_delivery task Retrieve creative delivery data with variant-level metrics. Requirements:

Agents MUST return delivery data for the requested creatives
Agents SHOULD include variant-level breakdowns when available
Sales agents implementing the Creative Protocol SHOULD support this task when their products generate or optimize creative variants

Error handling

Creative agents MUST return errors using the standard AdCP error schema. Common error codes:

REFERENCE_NOT_FOUND: Requested format does not exist or is not accessible (error.field identifies the format_id)
VALIDATION_ERROR: Manifest failed format validation
ASSET_MISSING: Required asset not provided in manifest
ASSET_INVALID: Asset does not meet format constraints
GENERATION_FAILED: Creative generation could not be completed

Security considerations

Transport security

All Creative Protocol communications MUST use HTTPS with TLS 1.2 or higher.

Asset security

Creative agents SHOULD validate that asset URLs are accessible
Creative agents SHOULD scan assets for malware and malicious content
Creative agents MUST NOT execute untrusted JavaScript during validation

Preview security

Preview URLs SHOULD be time-limited (indicated by expires_at)
Preview URLs MUST NOT depend on pod-local or process-local state unless the agent can guarantee that state for the advertised lifetime of the URL
Creative agents SHOULD sandbox HTML previews to prevent script execution
Consumers of output_format: "html" MUST only use trusted creative agents

Conformance

Creative agent conformance

A conformant Creative Protocol agent MUST:

Support at least one specified transport (MCP or A2A)
Implement list_creative_formats for format discovery
Return authoritative format definitions only for formats it owns
Validate manifests against format specifications
Use specified error codes

A conformant Creative Protocol agent SHOULD:

Implement build_creative for creative generation
Implement preview_creative for preview rendering
Support universal macros in tracking URLs
Implement list_creatives when the agent hosts a creative library
Implement sync_creatives when the agent accepts creative uploads
Support creative_id in build_creative when the agent hosts a creative library
Implement the accounts protocol (sync_accounts / list_accounts) when hosting a creative library
Declare supports_generation, supports_transformation, and has_creative_library in get_adcp_capabilities so buyers can determine the correct interaction model

Consumer conformance

A conformant Creative Protocol consumer MUST:

Use the agent_url from format IDs to identify the authoritative creative agent
Validate manifests against format specifications before submission
Handle validation errors appropriately
Track visited URLs when recursively discovering formats to avoid infinite loops

Implementation notes

Response time expectations

Creative agents SHOULD target the following response times:

Operation Type	Target Latency
Format listing (list_creative_formats)	< 1 second
Library query (list_creatives)	< 1 second
Creative sync (sync_creatives)	< 5 seconds
Preview generation (preview_creative)	< 5 seconds
Batch preview (10 creatives)	< 10 seconds
Creative generation (build_creative)	< 60 seconds

Recursive format discovery

Creative agents MAY reference other creative agents in their list_creative_formats response:

{
  "creative_agents": [{
    "agent_url": "https://creative.adcontextprotocol.org",
    "agent_name": "AdCP Reference Creative Agent",
    "capabilities": ["validation", "assembly", "preview"]
  }]
}

Consumers MAY recursively query referenced agents to discover additional formats. Consumers MUST track visited URLs to prevent infinite loops during recursive discovery.

Format-aware validation

Manifest validation MUST be performed in the context of the format specification:

Look up the format definition from the authoritative creative agent
For each asset in the manifest, find the corresponding entry in the format’s assets array
Validate the asset value against the type and constraints defined in the format

The format definition determines what type each asset_id should be. Asset type information is NOT included in the manifest itself.

Standard vs custom formats

Standard formats: Based on IAB specifications, hosted by the reference creative agent (https://creative.adcontextprotocol.org)
Custom formats: Defined by individual publishers or creative platforms for specialized inventory

Both work identically—the agent_url field identifies which agent is authoritative for each format.

Schema reference

Some creative protocol schemas (build_creative, list_creative_formats, preview_creative) have paths under media-buy/ because they were originally released as part of the media-buy protocol. The schema paths are stable identifiers and do not affect which protocol the task belongs to.

Schema	Description
`core/format.json`	Format definition
`core/creative-manifest.json`	Creative manifest
`core/creative-asset.json`	Asset definition
`media-buy/list-creative-formats-request.json`	list_creative_formats request
`media-buy/list-creative-formats-response.json`	list_creative_formats response
`creative/list-creatives-request.json`	list_creatives request
`creative/list-creatives-response.json`	list_creatives response
`creative/sync-creatives-request.json`	sync_creatives request
`creative/sync-creatives-response.json`	sync_creatives response

​Abstract

​Protocol overview

​Transport requirements

​Core concepts

​Creative agents

​Interaction models

​Format authority

​Formats

​Assets

​Manifests

​Universal macros

​Creative Status Lifecycle

​Lifecycle webhooks

​Pricing

​Pricing discovery surfaces

​Pricing flow

​Pricing models

​Consumption details

​Accounts requirement

​Bundled mode

​Tasks

​list_creative_formats

​list_transformers

​build_creative

​preview_creative

​list_creatives

​sync_creatives

​get_creative_delivery

​Error handling

​Security considerations

​Transport security

​Asset security

​Preview security

​Conformance

​Creative agent conformance

​Consumer conformance

​Implementation notes

​Response time expectations

​Recursive format discovery

​Format-aware validation

​Standard vs custom formats

​Schema reference

Abstract

Protocol overview

Transport requirements

Core concepts

Creative agents

Interaction models

Format authority

Formats

Assets

Manifests

Universal macros

Creative Status Lifecycle

Lifecycle webhooks

Pricing

Pricing discovery surfaces

Pricing flow

Pricing models

Consumption details

Accounts requirement

Bundled mode

Tasks

list_creative_formats

list_transformers

build_creative

preview_creative

list_creatives

sync_creatives

get_creative_delivery

Error handling

Security considerations

Transport security

Asset security

Preview security

Conformance

Creative agent conformance

Consumer conformance

Implementation notes

Response time expectations

Recursive format discovery

Format-aware validation

Standard vs custom formats

Schema reference