Skip to main content
Creative formats define the structural and technical requirements used to instantiate advertising creatives. A format specifies:
  • The media family under which the format falls (e.g., Display, Video, Audio, Native)
  • The creative element roles required to instantiate the format
  • Technical constraints such as duration, dimensions, file types, and limits
  • How the resulting creative is delivered and validated
Formats define requirements and constraints, not brand content or layout logic. For an overview of how formats, manifests, and creative agents work together, see the Creative Protocol Overview.

​
Standard vs Custom Formats

AdCP supports two categories of formats based on authority and reuse, not capability.

​
Standard Formats

Standard formats are predefined specifications provided by the AdCP Reference Creative Agent (https://creative.adcontextprotocol.org). Standard formats are:
  • Industry-aligned: Based on IAB format families and widely adopted conventions
  • Portable: Designed to work consistently across platforms
  • Validated: Pre-tested against known technical constraints
  • Discoverable: Returned via list_creative_formats
  • Maintained: Centrally documented and updated
Standard formats typically cover common use cases such as:
  • Display formats with fixed or responsive dimensions
  • Video formats with standard durations and aspect ratios
  • Audio formats with defined spot lengths
  • Common DOOH display and video executions
Guidance for sales agents: Before defining custom formats, check whether an equivalent standard format already exists. Most publishers can reference standard formats for common inventory and reserve custom formats for genuinely differentiated offerings. See Implementing Standard Format Support for detailed guidance.

​
Custom Formats

Custom formats are defined by publishers or platforms for inventory that cannot be accurately represented by standard formats. Custom formats may be used when there are:
  • Unique constraints: Non-standard dimensions, physical displays, or asset requirements
  • Specialized capabilities: Platform-specific rendering or interaction support
  • Premium inventory: Differentiated or bespoke ad products
  • Custom validation logic: Publisher-specific review or assembly rules
Custom formats should be introduced only when necessary. Where possible, standard formats should be reused to maximize portability and buyer understanding.

​
Discovering Formats

Buyers discover supported formats using the list_creative_formats task exposed by sales agents. Formats may be sourced from:
  • The sales agent itself - for custom formats
  • Referenced creative agents - such as the AdCP reference agent, for standard formats
Example discovery response: 
{
  "$schema": "https://adcontextprotocol.org/schemas/v2/creative/list-creative-formats-response.json",
  "formats": [
    {
      "format_id": {
        "agent_url": "https://youragent.com",
        "id": "homepage_takeover_2024"
      },
      "name": "Homepage Takeover",
      "type": "rich_media"
    }
  ],
  "creative_agents": [
    {
      "agent_url": "https://creative.adcontextprotocol.org"
    }
  ]
}
This indicates that the sales agent supports its own custom format and all formats defined by the referenced creative agent. For sales agents implementing format support: See Implementing Standard Format Support.

​
Format Authority

Each format includes an agent_url that identifies the authoritative creative agent responsible for the format: 
{
  "format_id": {
    "agent_url": "https://creative.adcontextprotocol.org",
    "id": "video_30s_hosted"
  },
  "name": "Standard 30-Second Video"
}
The authoritative creative agent provides:
  • Complete format specifications
  • Creative element requirements and constraints
  • Validation rules
  • Preview generation
  • Canonical documentation
Buyers and sales agents rely on the agent_url to retrieve definitive format information.

​
Format Visual Presentation

Formats may optionally include metadata to support visual browsing and selection in user interfaces.

​
Example Showcase

Field: example_url Purpose: Deep link to a publisher-controlled showcase May include:
  • Interactive demos
  • Videos
  • Multiple creative examples
  • Best practices and specifications
This approach allows publishers to present complex formats without constraining presentation in the protocol. Example: 
{
  "$schema": "https://adcontextprotocol.org/schemas/v2/core/format.json",
  "format_id": {
    "agent_url": "https://publisher.com",
    "id": "homepage_takeover_premium"
  },
  "name": "Premium Homepage Takeover",
  "type": "rich_media",
  "description": "Full-screen immersive experience with video, carousel, and companion units",
  "example_url": "https://publisher.com/formats/homepage-takeover-demo"
}

​
Referencing Formats

AdCP uses structured format identifiers everywhere to avoid ambiguity and namespace collisions.

​
Structured Format IDs (Required Everywhere)

ALL format references use structured format ID objects: 
{
  "$schema": "https://adcontextprotocol.org/schemas/v2/core/format-id.json",
  "agent_url": "https://creative.adcontextprotocol.org",
  "id": "display_300x250"
}
This approach ensures:
  • Explicit namespacing
  • Collision-safe identifiers
  • Schema validation
  • Extensibility without breaking changes
String-based format identifiers MUST NOT be used in API contracts.

​
Where Structured Format IDs Are Used

Requests:
  • sync_creatives - Uploading creative assets
  • build_creative - Generating creatives via creative agents
  • preview_creative - Preview generation
  • create_media_buy - When specifying format requirements
Responses:
  • list_creatives - Returning creative details
  • get_products - Product format capabilities
  • list_creative_formats - Format definitions
  • Any response containing creative or format details
Filter parameters:
  • format_ids (plural) in request filters - Array of structured format_id objects

​
Validation Rules

All AdCP agents MUST:
  1. ✅ Accept structured format_id objects in ALL contexts
  2. ✅ Return structured format_id objects in ALL responses
  3. ❌ Reject string format_ids with clear error messages
  4. ❌ Never use string format_ids in any API contract
Error handling for invalid format_id: 
{
  "error": "invalid_format_id",
  "message": "format_id must be a structured object with 'agent_url' and 'id' fields",
  "received": "display_300x250",
  "required_structure": {
    "agent_url": "https://creative-agent-url.com",
    "id": "display_300x250"
  }
}

​
Legacy Considerations

Some legacy systems may send string format_ids. Implementers have two options:
  1. Strict validation (recommended): Reject strings immediately with clear error
  2. Auto-upgrade with deprecation: Accept strings temporarily, log warnings, set removal timeline
If auto-upgrading, you MUST:
  • Only accept strings for well-known formats you can map to agent URLs
  • Fail loudly for unknown format strings
  • Log deprecation warnings on every request
  • Set and communicate a removal date (recommend 6 months maximum)

​
Format Structure

Formats are JSON objects with the following key fields: 
{
  "$schema": "https://adcontextprotocol.org/schemas/v2/core/format.json",
  "format_id": {
    "agent_url": "https://creative.adcontextprotocol.org",
    "id": "video_30s_hosted"
  },
  "name": "30-Second Hosted Video",
  "type": "video",
  "assets": [
    {
      "item_type": "individual",
      "asset_id": "video_file",
      "asset_type": "video",
      "asset_role": "hero_video",
      "required": true,
      "requirements": {
        "duration": "30s",
        "format": ["MP4"],
        "resolution": ["1920x1080", "1280x720"]
      }
    },
    {
      "item_type": "individual",
      "asset_id": "end_card_image",
      "asset_type": "image",
      "asset_role": "end_card",
      "required": false,
      "requirements": {
        "dimensions": "1920x1080",
        "format": ["PNG", "JPG"]
      }
    },
    {
      "item_type": "individual",
      "asset_id": "companion_banner",
      "asset_type": "image",
      "asset_role": "companion",
      "required": false,
      "requirements": {
        "dimensions": "300x250",
        "format": ["PNG", "JPG", "GIF"]
      }
    },
    {
      "item_type": "individual",
      "asset_id": "impression_tracker",
      "asset_type": "url",
      "asset_role": "third_party_tracking",
      "required": false,
      "requirements": {
        "description": "Third-party impression tracking pixel URL"
      }
    }
  ],

  // DEPRECATED: Use "assets" above instead. Kept for backward compatibility.
  "assets": [
    {
      "item_type": "individual",
      "asset_id": "video_file",
      "asset_type": "video",
      "asset_role": "hero_video",
      "requirements": {
        "duration": "30s",
        "format": ["MP4"],
        "resolution": ["1920x1080", "1280x720"]
      }
    }
  ]
}
Key fields:
  • format_id: Unique identifier (may be namespaced with domain:id)
  • agent_url: The creative agent authoritative for this format
  • type: Category (video, display, audio, native, dooh, rich_media)
  • assets: Array of all asset specifications with required boolean indicating mandatory vs optional
  • asset_role: Identifies asset purpose (hero_image, logo, cta_button, etc.)
  • renders: Array of rendered outputs with dimensions - see below

​
Asset Discovery

The assets array enables comprehensive asset discovery. Each asset has a required boolean:
  • required: true - Asset MUST be provided for a valid creative
  • required: false - Asset is optional, enhances the creative when provided (e.g., companion banners, third-party tracking pixels)
This unified approach helps creative tools and AI agents understand the full capabilities of a format, enabling richer creative experiences when optional assets are available while clearly indicating minimum requirements.

​
Rendered Outputs and Dimensions

Formats describe one or more rendered outputs, each with defined dimensions and semantic roles. This supports:
  • Single-render formats
  • Companion creatives
  • Multi-placement outputs
  • Responsive behavior
  • Physical dimensions for non-personal environments
Formats specify their rendered outputs via the renders array. Most formats produce a single render, but some (companion ads, adaptive formats, multi-placement) produce multiple renders: 
{
  "$schema": "https://adcontextprotocol.org/schemas/v2/core/format.json",
  "format_id": {
    "agent_url": "https://creative.adcontextprotocol.org",
    "id": "display_300x250"
  },
  "name": "Display Banner 300x250",
  "type": "display",
  "renders": [
    {
      "role": "primary",
      "dimensions": {
        "width": 300,
        "height": 250,
        "responsive": {
          "width": false,
          "height": false
        }
      }
    }
  ]
}
Multi-render example (companion ad): 
{
  "$schema": "https://adcontextprotocol.org/schemas/v2/core/format.json",
  "format_id": {
    "agent_url": "https://creative.adcontextprotocol.org",
    "id": "video_with_companion_300x250"
  },
  "name": "Video with Companion Banner",
  "type": "video",
  "renders": [
    {
      "role": "primary",
      "dimensions": {
        "width": 1920,
        "height": 1080,
        "responsive": {
          "width": false,
          "height": false
        }
      }
    },
    {
      "role": "companion",
      "dimensions": {
        "width": 300,
        "height": 250,
        "responsive": {
          "width": false,
          "height": false
        }
      }
    }
  ]
}
Dimension types: Fixed dimensions (standard display ads): 
{
  "role": "primary",
  "dimensions": {
    "width": 300,
    "height": 250,
    "responsive": {"width": false, "height": false},
    "unit": "px"
  }
}
Responsive width (fluid banners): 
{
  "role": "primary",
  "dimensions": {
    "min_width": 300,
    "max_width": 970,
    "height": 250,
    "responsive": {"width": true, "height": false},
    "unit": "px"
  }
}
Aspect ratio constrained (native formats): 
{
  "role": "primary",
  "dimensions": {
    "aspect_ratio": "16:9",
    "min_width": 300,
    "responsive": {"width": true, "height": true},
    "unit": "px"
  }
}
Physical dimensions (DOOH): 
{
  "role": "primary",
  "dimensions": {
    "width": 48,
    "height": 14,
    "responsive": {"width": false, "height": false},
    "unit": "inches"
  }
}
Benefits of the renders structure:
  • Supports single and multi-render formats uniformly
  • No string parsing required - structured dimensions
  • Schema-validated dimensions
  • Supports responsive and fixed formats equally
  • Enables proper preview rendering
  • Allows dimension-based filtering
  • Supports physical units for DOOH
  • Clear semantic roles for each rendered piece

​
Format Categories

Formats are classified under IAB format families:
  • Display
  • Video
  • Audio
  • Native
Additional distinctions such as DOOH, CTV, or mobile describe delivery environments, not format families. AdCP supports formats across multiple media types:

​
Video Formats

  • Standard video (15s, 30s, 60s)
  • Vertical video for mobile/stories
  • VAST/VPAID tags
  • Interactive video
See Video Channel Guide for complete specifications.

​
Display Formats

  • Standard IAB sizes (300x250, 728x90, etc.)
  • Responsive units
  • Rich media and expandable
  • HTML5 creative
See Display Channel Guide for complete specifications.

​
Audio Formats

  • Streaming audio (15s, 30s, 60s)
  • Podcast insertion
  • Companion banners
  • VAST audio tags
See Audio Channel Guide for complete specifications.

​
DOOH Formats

  • Digital billboards
  • Transit displays
  • Retail screens
  • Venue-based impression tracking
See DOOH Channel Guide for complete specifications.

​
Carousel/Multi-Asset Formats

  • Product carousels (3-10 items)
  • Story sequences
  • Slideshow formats
  • Frame-based structures
See Carousel Channel Guide for complete specifications.

​
Multi-Asset & Frame-Based Formats

Some formats like carousels, slideshows, and stories use repeatable asset groups where each frame contains a collection of assets. See the Carousel & Multi-Asset Formats guide for complete documentation on frame-based format patterns.

​
Format Cards

Format cards provide visual representations of creative formats for display in browsing and selection interfaces. Creative agents can optionally include card definitions that reference card formats and provide the assets needed to render attractive visual cards.

​
Card Types

Creative agents should provide at least the standard card, and optionally a detailed card: Standard Card (format_card):
  • Compact 300x400px card for format browsing
  • Supports 2x density images for retina displays
  • Quick visual understanding of format specs
Detailed Card (format_card_detailed, optional):
  • Responsive layout with text description alongside hero carousel showing format in context
  • Markdown specifications section below
  • Full format documentation similar to Yahoo’s ad specs

​
Structure

{
  "format_id": {
    "agent_url": "https://creative.adcontextprotocol.org",
    "id": "video_standard_30s"
  },
  "name": "Standard Video - 30 seconds",
  "type": "video",
  // ... other format fields ...

  "format_card": {
    "format_id": {
      "agent_url": "https://creative.adcontextprotocol.org",
      "id": "format_card_standard"
    },
    "manifest": {
      "display_name": "30-Second Video",
      "preview_mockup_url": "https://cdn.example.com/format-mockups/video_30s.png",
      "format_type_label": "Video"
    }
  },

  "format_card_detailed": {
    "format_id": {
      "agent_url": "https://creative.adcontextprotocol.org",
      "id": "format_card_detailed"
    },
    "manifest": {
      "display_name": "Standard 30-Second Video",
      "description": "The Edge A-Logs Horizon (desktop) format is an encompassing...",
      "carousel_images": [
        "https://cdn.example.com/formats/video_30s_context1.jpg",
        "https://cdn.example.com/formats/video_30s_context2.jpg"
      ],
      "specifications_markdown": "# Technical Specifications\n\n..."
    }
  }
}

​
Rendering Cards

Cards can be rendered in two ways:
  1. Via preview_creative: Pass the card format and manifest to generate a rendered card
  2. Pre-rendered: Creative agents can pre-generate cards and serve them directly
This flexibility allows implementations to choose between dynamic generation or static hosting based on their infrastructure.

​
Standard Card Formats

The AdCP reference creative agent defines two standard card formats:
  • format_card_standard (300x400px) - Compact card for format browsing
  • format_card_detailed (responsive) - Rich card with carousel and full specs
Creative agents can also define custom card formats to highlight unique format capabilities or match their branding. Note: Standard card format definitions are maintained in the creative-agent repository, not in this protocol specification.

​
When to Include Format Cards

Format cards are optional but recommended for:
  • Visual formats (display, video, DOOH) where mockups help explain the format
  • Complex formats with multiple asset requirements
  • Custom formats that differ from standard specifications
  • Formats where visual preview aids buyer understanding
Use the detailed card variant when you want to provide comprehensive format documentation similar to ad spec pages.

​
Client Rendering Guidelines

When displaying formats in UIs, clients should follow this fallback order:
  1. If format_card exists → Render card via preview_creative or display pre-rendered image
  2. If no format_card exists → Render text-only representation (format name + description)
  3. If card rendering fails → Gracefully fall back to text-only representation
This ensures a consistent user experience regardless of what format metadata is available.