Creative Specification

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Abstract

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Protocol overview

• 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

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Transport requirements

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

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Core concepts

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Creative agents

• 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

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Interaction models

• 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)

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Format authority

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

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Formats

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

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Assets

• 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

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Manifests

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

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Universal macros

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

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Tasks

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list_creative_formats

• 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

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build_creative

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

• 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.

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preview_creative

• Creative agents MUST validate manifests before generating previews
• Creative agents MUST return preview URLs or HTML for valid manifests
• Creative agents MUST include expires_at for preview URLs
• Creative agents SHOULD support batch preview for multiple creatives
• Creative agents MAY support multiple output formats (URL, HTML, image)

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list_creatives

• 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.

• Creative agents that host a library SHOULD implement the accounts protocol (sync_accounts / list_accounts) 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

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sync_creatives

• 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

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get_creative_delivery

• 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

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Error handling

• FORMAT_NOT_FOUND: Requested format does not exist
• 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

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Security considerations

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Transport security

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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

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Preview security

• Preview URLs SHOULD be time-limited (indicated by expires_at)
• Creative agents SHOULD sandbox HTML previews to prevent script execution
• Consumers of output_format: "html" MUST only use trusted creative agents

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Conformance

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Creative agent conformance

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

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

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Consumer conformance

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

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Implementation notes

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Response time expectations

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Recursive format discovery

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

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Format-aware validation

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

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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

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Schema reference