Carousel & Multi-Asset Formats

This guide covers how AdCP represents carousel and multi-asset advertising formats that display multiple items in sequence: product carousels, image slideshows, story sequences, and video playlists.

Carousel Format Characteristics

Carousel formats use repeatable asset groups to represent:

Product Carousels - Multiple products with images, titles, and prices
Image Slideshows - Series of images with optional captions
Story Sequences - Sequential narrative frames (mobile stories)
Video Playlists - Multiple video clips displayed in sequence

All carousel formats use asset_group_id with item_type: "repeatable_group", min_count, and max_count to define the structure.

Repeatable Asset Groups

Basic Structure

Carousel formats define a repeatable asset group containing the assets for each item:

{
  "format_id": {
    "agent_url": "https://creative.adcontextprotocol.org",
    "id": "product_carousel_3_to_10"
  },
  "type": "display",
  "dimensions": "300x250",
  "assets_required": [
    {
      "item_type": "repeatable_group",
      "asset_group_id": "product",
      "min_count": 3,
      "max_count": 10,
      "assets": [
        {
          "asset_id": "image",
          "asset_type": "image",
          "asset_role": "product_image",
          "requirements": {
            "width": 300,
            "height": 300,
            "aspect_ratio": "1:1"
          }
        },
        {
          "asset_id": "title",
          "asset_type": "text",
          "requirements": {"max_length": 50}
        },
        {
          "asset_id": "price",
          "asset_type": "text",
          "requirements": {"max_length": 20}
        }
      ]
    },
    {
      "item_type": "individual",
      "asset_id": "brand_logo",
      "asset_type": "image",
      "requirements": {"width": 80, "height": 80}
    }
  ]
}

Standard Carousel Formats

Product Carousel (Display)

{
  "format_id": {
    "agent_url": "https://creative.adcontextprotocol.org",
    "id": "product_carousel_display"
  },
  "type": "display",
  "dimensions": "300x600",
  "assets_required": [
    {
      "item_type": "repeatable_group",
      "asset_group_id": "product",
      "min_count": 2,
      "max_count": 5,
      "assets": [
        {
          "asset_id": "image",
          "asset_type": "image",
          "asset_role": "product_image",
          "requirements": {"width": 300, "height": 250}
        },
        {
          "asset_id": "title",
          "asset_type": "text",
          "requirements": {"max_length": 40}
        },
        {
          "asset_id": "description",
          "asset_type": "text",
          "requirements": {"max_length": 100}
        },
        {
          "asset_id": "cta_text",
          "asset_type": "text",
          "requirements": {"max_length": 15}
        }
      ]
    }
  ]
}

Image Slideshow

{
  "format_id": {
    "agent_url": "https://creative.adcontextprotocol.org",
    "id": "image_slideshow_5s_each"
  },
  "type": "display",
  "dimensions": "728x90",
  "assets_required": [
    {
      "item_type": "repeatable_group",
      "asset_group_id": "slide",
      "min_count": 3,
      "max_count": 8,
      "assets": [
        {
          "asset_id": "image",
          "asset_type": "image",
          "requirements": {"width": 728, "height": 90}
        },
        {
          "asset_id": "caption",
          "asset_type": "text",
          "required": false,
          "requirements": {"max_length": 60}
        }
      ]
    }
  ]
}

Story Sequence (Mobile)

{
  "format_id": {
    "agent_url": "https://creative.adcontextprotocol.org",
    "id": "mobile_story_vertical"
  },
  "type": "display",
  "dimensions": "1080x1920",
  "assets_required": [
    {
      "item_type": "repeatable_group",
      "asset_group_id": "frame",
      "min_count": 3,
      "max_count": 7,
      "assets": [
        {
          "asset_id": "background",
          "asset_type": "image",
          "asset_role": "background_image",
          "requirements": {
            "width": 1080,
            "height": 1920,
            "aspect_ratio": "9:16"
          }
        },
        {
          "asset_id": "headline",
          "asset_type": "text",
          "requirements": {"max_length": 30}
        },
        {
          "asset_id": "body",
          "asset_type": "text",
          "requirements": {"max_length": 100}
        }
      ]
    },
    {
      "item_type": "individual",
      "asset_id": "brand_logo",
      "asset_type": "image",
      "requirements": {"width": 100, "height": 100}
    }
  ]
}

Video Playlist

{
  "format_id": {
    "agent_url": "https://creative.adcontextprotocol.org",
    "id": "video_playlist_6s_bumpers"
  },
  "type": "video",
  "assets_required": [
    {
      "item_type": "repeatable_group",
      "asset_group_id": "clip",
      "min_count": 2,
      "max_count": 5,
      "assets": [
        {
          "asset_id": "video",
          "asset_type": "video",
          "requirements": {
            "duration": "6s",
            "format": "MP4 H.264",
            "resolution": ["1920x1080"]
          }
        }
      ]
    }
  ]
}

Creative Manifests

Naming Convention

Assets in manifests use the pattern: {group_id}_{index}_{asset_id} Indexing is zero-based: product_0_image, product_1_image, product_2_image Example: For a format with asset_group_id: "product" and asset_id: "image", the manifest provides:

First item: product_0_image
Second item: product_1_image
Third item: product_2_image

All assets for a given index must be provided together (you cannot have product_0_image without product_0_title if title is required).

Product Carousel Manifest

{
  "format_id": {
    "agent_url": "https://creative.adcontextprotocol.org",
    "id": "product_carousel_3_to_10"
  },
  "assets": {
    "product_0_image": {
      "asset_type": "image",
      "url": "https://cdn.brand.com/products/shoes_red.jpg",
      "width": 300,
      "height": 300
    },
    "product_0_title": {
      "asset_type": "text",
      "content": "Red Running Shoes"
    },
    "product_0_price": {
      "asset_type": "text",
      "content": "$89.99"
    },
    "product_1_image": {
      "asset_type": "image",
      "url": "https://cdn.brand.com/products/shoes_blue.jpg",
      "width": 300,
      "height": 300
    },
    "product_1_title": {
      "asset_type": "text",
      "content": "Blue Trail Shoes"
    },
    "product_1_price": {
      "asset_type": "text",
      "content": "$79.99"
    },
    "product_2_image": {
      "asset_type": "image",
      "url": "https://cdn.brand.com/products/shoes_black.jpg",
      "width": 300,
      "height": 300
    },
    "product_2_title": {
      "asset_type": "text",
      "content": "Black Casual Shoes"
    },
    "product_2_price": {
      "asset_type": "text",
      "content": "$69.99"
    },
    "brand_logo": {
      "asset_type": "image",
      "url": "https://cdn.brand.com/logo.png",
      "width": 80,
      "height": 80
    },
    "landing_url": {
      "asset_type": "url",
      "url_type": "clickthrough",
      "url": "https://brand.com/shoes?campaign={MEDIA_BUY_ID}"
    }
  }
}

Story Sequence Manifest

{
  "format_id": {
    "agent_url": "https://creative.adcontextprotocol.org",
    "id": "mobile_story_vertical"
  },
  "assets": {
    "frame_0_background": {
      "asset_type": "image",
      "url": "https://cdn.brand.com/story_frame1.jpg",
      "width": 1080,
      "height": 1920
    },
    "frame_0_headline": {
      "asset_type": "text",
      "content": "New Collection"
    },
    "frame_0_body": {
      "asset_type": "text",
      "content": "Discover our latest summer styles"
    },
    "frame_1_background": {
      "asset_type": "image",
      "url": "https://cdn.brand.com/story_frame2.jpg",
      "width": 1080,
      "height": 1920
    },
    "frame_1_headline": {
      "asset_type": "text",
      "content": "50% Off"
    },
    "frame_1_body": {
      "asset_type": "text",
      "content": "Limited time offer on all items"
    },
    "frame_2_background": {
      "asset_type": "image",
      "url": "https://cdn.brand.com/story_frame3.jpg",
      "width": 1080,
      "height": 1920
    },
    "frame_2_headline": {
      "asset_type": "text",
      "content": "Shop Now"
    },
    "frame_2_body": {
      "asset_type": "text",
      "content": "Tap to explore the collection"
    },
    "brand_logo": {
      "asset_type": "image",
      "url": "https://cdn.brand.com/logo.png",
      "width": 100,
      "height": 100
    },
    "landing_url": {
      "asset_type": "url",
      "url_type": "clickthrough",
      "url": "https://brand.com/summer-sale?device={DEVICE_ID}&campaign={MEDIA_BUY_ID}"
    }
  }
}

Manifest Validation Rules

Complete Groups Required

Each group instance must include all required assets defined in the format:

// ❌ INVALID - missing product_1_title
{
  "product_0_image": {...},
  "product_0_title": {...},
  "product_1_image": {...}
}

// ✅ VALID - all required assets present for each product
{
  "product_0_image": {...},
  "product_0_title": {...},
  "product_1_image": {...},
  "product_1_title": {...}
}

Count Constraints

Manifests must provide between min_count and max_count instances:

// Format specification
{
  "asset_group_id": "product",
  "min_count": 3,
  "max_count": 10
}

// ❌ INVALID - only 2 products (below minimum)
{
  "product_0_image": {...},
  "product_1_image": {...}
}

// ✅ VALID - 3 products (meets minimum)
{
  "product_0_image": {...},
  "product_1_image": {...},
  "product_2_image": {...}
}

Optional Assets

Individual assets within a group can be marked "required": false:

{
  "item_type": "repeatable_group",
  "asset_group_id": "slide",
  "min_count": 3,
  "max_count": 8,
  "assets": [
    {
      "asset_id": "image",
      "required": true
    },
    {
      "asset_id": "caption",
      "required": false  // Can be omitted
    }
  ]
}

Optional assets can be provided for some instances but not others:

{
  "slide_0_image": {...},
  "slide_0_caption": {...},  // Caption provided
  "slide_1_image": {...},    // No caption
  "slide_2_image": {...},
  "slide_2_caption": {...}   // Caption provided
}

Zero-Based Indexing

Always use sequential zero-based indexing starting from 0:

product_0_image
product_0_title
product_1_image
product_1_title
product_2_image
product_2_title

Clickthrough URL Patterns

Single Landing URL

All carousel items link to the same destination:

{
  "landing_url": {
    "asset_type": "url",
    "url_type": "clickthrough",
    "url": "https://brand.com/products?campaign={MEDIA_BUY_ID}"
  }
}

Per-Item Landing URLs

Each carousel item can have its own clickthrough URL (if supported by format):

{
  "product_0_landing_url": {
    "asset_type": "url",
    "url_type": "clickthrough",
    "url": "https://brand.com/product/shoes-red?campaign={MEDIA_BUY_ID}"
  },
  "product_1_landing_url": {
    "asset_type": "url",
    "url_type": "clickthrough",
    "url": "https://brand.com/product/shoes-blue?campaign={MEDIA_BUY_ID}"
  },
  "product_2_landing_url": {
    "asset_type": "url",
    "url_type": "clickthrough",
    "url": "https://brand.com/product/shoes-black?campaign={MEDIA_BUY_ID}"
  }
}

The format definition specifies whether per-item URLs are supported.

Carousel-Specific Macros

In addition to universal macros, some platforms support carousel-specific macros:

{CAROUSEL_INDEX} - Zero-based index of current carousel item
{CAROUSEL_POSITION} - One-based position (for user display)
{CAROUSEL_TOTAL} - Total number of items in carousel

Example tracking URL:

https://track.brand.com/view?buy={MEDIA_BUY_ID}&item={CAROUSEL_INDEX}&total={CAROUSEL_TOTAL}

Complete Example

Format Definition

{
  "format_id": {
    "agent_url": "https://creative.adcontextprotocol.org",
    "id": "ecommerce_carousel_300x600"
  },
  "name": "E-commerce Product Carousel",
  "type": "display",
  "dimensions": "300x600",
  "assets_required": [
    {
      "item_type": "repeatable_group",
      "asset_group_id": "product",
      "min_count": 3,
      "max_count": 6,
      "assets": [
        {
          "asset_id": "image",
          "asset_type": "image",
          "asset_role": "product_image",
          "requirements": {
            "width": 300,
            "height": 300,
            "aspect_ratio": "1:1",
            "file_types": ["jpg", "png", "webp"]
          }
        },
        {
          "asset_id": "title",
          "asset_type": "text",
          "requirements": {"max_length": 50}
        },
        {
          "asset_id": "price",
          "asset_type": "text",
          "requirements": {"max_length": 20}
        },
        {
          "asset_id": "discount_badge",
          "asset_type": "text",
          "required": false,
          "requirements": {"max_length": 10}
        }
      ]
    },
    {
      "item_type": "individual",
      "asset_id": "brand_logo",
      "asset_type": "image",
      "requirements": {"width": 80, "height": 80}
    },
    {
      "item_type": "individual",
      "asset_id": "cta_text",
      "asset_type": "text",
      "requirements": {"max_length": 15}
    }
  ]
}

Manifest

{
  "format_id": {
    "agent_url": "https://creative.adcontextprotocol.org",
    "id": "ecommerce_carousel_300x600"
  },
  "assets": {
    "product_0_image": {
      "asset_type": "image",
      "url": "https://cdn.brand.com/products/watch_gold.jpg",
      "width": 300,
      "height": 300
    },
    "product_0_title": {
      "asset_type": "text",
      "content": "Gold Classic Watch"
    },
    "product_0_price": {
      "asset_type": "text",
      "content": "$299"
    },
    "product_0_discount_badge": {
      "asset_type": "text",
      "content": "25% OFF"
    },
    "product_1_image": {
      "asset_type": "image",
      "url": "https://cdn.brand.com/products/watch_silver.jpg",
      "width": 300,
      "height": 300
    },
    "product_1_title": {
      "asset_type": "text",
      "content": "Silver Sport Watch"
    },
    "product_1_price": {
      "asset_type": "text",
      "content": "$249"
    },
    "product_2_image": {
      "asset_type": "image",
      "url": "https://cdn.brand.com/products/watch_leather.jpg",
      "width": 300,
      "height": 300
    },
    "product_2_title": {
      "asset_type": "text",
      "content": "Leather Dress Watch"
    },
    "product_2_price": {
      "asset_type": "text",
      "content": "$199"
    },
    "product_2_discount_badge": {
      "asset_type": "text",
      "content": "NEW"
    },
    "brand_logo": {
      "asset_type": "image",
      "url": "https://cdn.brand.com/logo.png",
      "width": 80,
      "height": 80
    },
    "cta_text": {
      "asset_type": "text",
      "content": "Shop Now"
    },
    "landing_url": {
      "asset_type": "url",
      "url_type": "clickthrough",
      "url": "https://brand.com/watches?campaign={MEDIA_BUY_ID}&utm_source={DOMAIN}"
    },
    "impression_tracker": {
      "asset_type": "url",
      "url_type": "tracker",
      "url": "https://track.brand.com/imp?buy={MEDIA_BUY_ID}&cb={CACHEBUSTER}"
    }
  }
}

Creative Manifests - Complete manifest specification
Universal Macros - Supported macros for tracking
Asset Types - Asset type specifications
Display Ads - Standard display formats
Video Ads - Video format specifications

Getting Started

Protocols

Signals Protocol

Curation Protocol

Media Buy Protocol

Creative

Reference

Carousel & Multi-Asset Formats

Carousel & Multi-Asset Formats

Carousel Format Characteristics

Repeatable Asset Groups

Basic Structure

Standard Carousel Formats

Product Carousel (Display)

Image Slideshow

Story Sequence (Mobile)

Video Playlist

Creative Manifests

Naming Convention

Product Carousel Manifest

Story Sequence Manifest

Manifest Validation Rules

Complete Groups Required

Count Constraints

Optional Assets

Zero-Based Indexing

Clickthrough URL Patterns

Single Landing URL

Per-Item Landing URLs

Carousel-Specific Macros

Complete Example

Format Definition

Manifest

Getting Started

Protocols

Signals Protocol

Curation Protocol

Media Buy Protocol

Creative

Reference

​Carousel & Multi-Asset Formats

​Carousel Format Characteristics

​Repeatable Asset Groups

​Basic Structure

​Standard Carousel Formats

​Product Carousel (Display)

​Image Slideshow

​Story Sequence (Mobile)

​Video Playlist

​Creative Manifests

​Naming Convention

​Product Carousel Manifest

​Story Sequence Manifest

​Manifest Validation Rules

​Complete Groups Required

​Count Constraints

​Optional Assets

​Zero-Based Indexing

​Clickthrough URL Patterns

​Single Landing URL

​Per-Item Landing URLs

​Carousel-Specific Macros

​Complete Example

​Format Definition

​Manifest

​Related Documentation

Carousel & Multi-Asset Formats

Carousel Format Characteristics

Repeatable Asset Groups

Basic Structure

Standard Carousel Formats

Product Carousel (Display)

Image Slideshow

Story Sequence (Mobile)

Video Playlist

Creative Manifests

Naming Convention

Product Carousel Manifest

Story Sequence Manifest

Manifest Validation Rules

Complete Groups Required

Count Constraints

Optional Assets

Zero-Based Indexing

Clickthrough URL Patterns

Single Landing URL

Per-Item Landing URLs

Carousel-Specific Macros

Complete Example

Format Definition

Manifest

Related Documentation