> ## Documentation Index
> Fetch the complete documentation index at: https://docs.adcontextprotocol.org/llms.txt
> Use this file to discover all available pages before exploring further.

# Implementing Standard Format Support

> Implementing standard creative formats in AdCP — reference IAB formats from the AdCP creative reference agent instead of redefining display, video, and native specs.

This guide is for **sales agents** implementing creative format support. Before creating custom format definitions, you should check what formats are already available in the AdCP ecosystem.

## Implementation Philosophy: Check First, Then Extend

Most publishers support some combination of standard formats - whether IAB standard sizes, common video specs, or widely-used native formats. Rather than defining these yourself:

1. **Check the reference creative agent** to see if your formats are already defined
2. **Reference the formats** if they match your needs
3. **Only create custom formats** when you have truly unique requirements

This approach:

* **Reduces maintenance burden** - No need to maintain format definitions that already exist
* **Enables creative portability** - Buyers can reuse creatives across publishers
* **Improves ecosystem consistency** - Everyone uses the same specifications for common formats

## The Reference Creative Agent

**URL:** `https://creative.adcontextprotocol.org`

**Status:** Production service - this is a real, working AdCP creative agent

The reference creative agent provides authoritative definitions for common creative formats used across the advertising industry:

* IAB standard display sizes (300x250, 728x90, 320x50, etc.)
* Standard video formats (15s, 30s, 60s pre-roll, etc.)
* Audio formats for streaming and podcast insertion
* DOOH formats for digital out-of-home
* Native formats for responsive placements
* Carousel formats for multi-product displays

**Before creating custom formats,** query the reference creative agent to see if the formats you need already exist.

## Why Use Standard Formats?

### For Sales Agents

* **No maintenance burden**: Don't replicate IAB standard format definitions
* **Ecosystem consistency**: Everyone uses the same format specifications
* **Focus on differentiation**: Spend time on custom formats unique to your inventory

### For Buyers

* **Portability**: One creative works across multiple publishers
* **Predictability**: Format requirements are consistent
* **Faster launches**: No custom creative production per publisher

## Implementation Steps

### Step 1: Discover What Formats You Need

List the creative formats your inventory accepts. For example:

* Display: 300x250, 728x90, 320x50
* Video: 15-second pre-roll, 30-second pre-roll
* Native: Responsive native format

### Step 2: Check the Reference Creative Agent

Query `https://creative.adcontextprotocol.org` using `list_creative_formats` to see which of your formats already exist. The reference agent maintains formats for:

* All IAB standard display sizes
* Common video durations and aspect ratios
* Standard audio formats
* DOOH specifications
* Native ad formats

### Step 3: Decide What to Reference vs Define

**Reference formats when:**

* The format matches your technical requirements exactly
* You accept creatives built to standard IAB specifications
* You want creative portability across publishers

**Define custom formats when:**

* You have unique technical requirements (custom dimensions, special asset needs)
* You need publisher-specific validation or assembly logic
* You offer premium, differentiated ad experiences

### Step 4: Implement Your Response

When implementing `list_creative_formats`, include the reference creative agent if you support any standard formats:

**Most Common: Reference Standard Formats**

If your inventory accepts standard formats (which most publishers do):

```json theme={null}
{
  "formats": [],
  "creative_agents": [
    "https://creative.adcontextprotocol.org"
  ]
}
```

This tells buyers: "We support all standard formats from the reference creative agent."

**With Custom Formats: Combine Both**

If you have unique formats PLUS standard format support:

```json theme={null}
{
  "formats": [
    {
      "format_id": {
        "agent_url": "https://youragent.com",
        "id": "homepage_takeover"
      },
      "name": "Homepage Takeover",
      "type": "rich_media",
      "assets": [...]
    }
  ],
  "creative_agents": [
    "https://creative.adcontextprotocol.org"
  ]
}
```

This tells buyers: "We support our custom homepage takeover format, PLUS all standard formats from the reference creative agent."

**Only Custom Formats: Skip the Reference**

If you ONLY support custom formats with truly unique requirements (rare):

```json theme={null}
{
  "formats": [
    {
      "format_id": {
        "agent_url": "https://youragent.com",
        "id": "custom_holographic_display"
      },
      "name": "Holographic Display Format",
      "type": "dooh",
      "assets": [...]
    }
  ]
}
```

**Note:** This is uncommon. Most publishers accept at least some standard formats (300x250, etc.) and should include the reference creative agent URL.

## What Standard Formats Are Included?

The reference creative agent provides formats across all major channels:

* **[Display Formats](/dist/docs/3.0.0-rc.2/creative/channels/display)** - IAB standard banner sizes (300x250, 728x90, 320x50, etc.)
* **[Video Formats](/dist/docs/3.0.0-rc.2/creative/channels/video)** - Standard video ad specifications (15s, 30s, vertical, CTV)
* **[Audio Formats](/dist/docs/3.0.0-rc.2/creative/channels/audio)** - Streaming audio and podcast insertion formats
* **[DOOH Formats](/dist/docs/3.0.0-rc.2/creative/channels/dooh)** - Digital out-of-home billboard and transit specs
* **[Carousel Formats](/dist/docs/3.0.0-rc.2/creative/channels/carousels)** - Multi-product and slideshow formats

Each format includes:

* Precise technical requirements (dimensions, duration, file types)
* Required and optional assets with specifications
* Universal macro support
* Preview and validation capabilities

## Format Discovery Flow

When buyers discover formats from your sales agent:

1. **Buyer calls** `list_creative_formats` on your sales agent
2. **Your response includes** custom formats plus `creative_agents: ["https://creative.adcontextprotocol.org"]`
3. **Buyer recursively queries** the reference agent to discover standard formats
4. **Buyer sees combined list** of your custom formats plus all standard formats

The buyer tracks which URLs they've queried to avoid infinite loops.

## Best Practices for Sales Agents

### ✅ DO Reference Standard Formats

```json theme={null}
{
  "creative_agents": [
    "https://creative.adcontextprotocol.org"
  ]
}
```

**When:** Your inventory accepts standard IAB sizes with no special requirements

**Why:** Reduces maintenance, ensures consistency, buyers already have compatible creatives

### ✅ DO Define Custom Formats

```json theme={null}
{
  "formats": [
    {
      "format_id": {
        "agent_url": "https://youragent.com",
        "id": "native_feed_card"
      },
      "type": "native"
    }
  ]
}
```

**When:** You have unique inventory experiences or specific technical requirements

**Why:** Enables differentiation and premium inventory

### ❌ DON'T Replicate Standard Formats

```json theme={null}
{
  "formats": [
    {"format_id": {"agent_url": "https://youragent.com", "id": "display_300x250"}},
    {"format_id": {"agent_url": "https://youragent.com", "id": "display_728x90"}},
    {"format_id": {"agent_url": "https://youragent.com", "id": "display_320x50"}},
    // ... copying 50+ standard formats
  ]
}
```

**Why not:** Maintenance burden, version drift, inconsistency across ecosystem

**Exception:** You need custom validation/preview logic for these formats

### ✅ DO Use Both When Appropriate

```json theme={null}
{
  "formats": [
    // Your differentiating formats
  ],
  "creative_agents": [
    "https://creative.adcontextprotocol.org"
  ]
}
```

**Result:** Buyers see your custom formats plus all standard formats

## Format ID Namespacing

To prevent conflicts when multiple agents define formats, AdCP uses a **namespace pattern** for format identifiers.

### Namespace Pattern: `{domain}:{format_id}`

**Structure:**

```
domain:format_id
```

**Examples:**

* `creative.adcontextprotocol.org:display_300x250`
* `creative.adcontextprotocol.org:video_30s_hosted`
* `youragent.com:homepage_takeover_2024`
* `publisher.example:native_feed_card`

### Domain Requirements

**The domain in a namespaced format\_id MUST:**

1. **Host a valid agent card** at `{domain}/.well-known/adagents.json`
2. **Declare MCP endpoint** in the agent card extension
3. **Declare A2A endpoint** in the standard agent card section

**Example agent card at** `https://youragent.com/.well-known/adagents.json`:

```json theme={null}
{
  "agents": [
    {
      "agent_url": "https://youragent.com",
      "agent_name": "Your Creative Agent",
      "protocols": ["mcp", "a2a"],
      "mcp_endpoint": "https://youragent.com/mcp",
      "a2a_endpoint": "https://youragent.com/a2a",
      "capabilities": ["list_creative_formats", "preview_creative"]
    }
  ]
}
```

This ensures the domain in the namespace is a valid, discoverable agent that can provide format specifications and validation.

### When to Use Namespaces

**Always use namespaced format\_ids** when defining formats:

```json theme={null}
{
  "$schema": "/schemas/3.0.0-rc.2/media-buy/list-creative-formats-response.json",
  "formats": [
    {
      "format_id": {
        "agent_url": "https://youragent.com",
        "id": "homepage_takeover"
      },
      "name": "Homepage Takeover",
      "type": "rich_media"
    }
  ]
}
```

**Benefits:**

* **No collisions** - Each agent owns its namespace
* **Clear ownership** - Domain identifies the authoritative agent
* **Discoverable** - Buyers can query the domain's agent card
* **Verifiable** - Domain must prove ownership via agent card

### Namespace Examples by Agent Type

**Reference Creative Agent:**

```json theme={null}
{
  "format_id": {
    "agent_url": "https://creative.adcontextprotocol.org",
    "id": "display_300x250"
  }
}
```

**Publisher Sales Agent:**

```json theme={null}
{
  "format_id": {
    "agent_url": "https://youragent.com",
    "id": "custom_format"
  }
}
```

**DCO Platform:**

```json theme={null}
{
  "format_id": {
    "agent_url": "https://dco.example",
    "id": "dynamic_creative_v2"
  }
}
```

### Conflict Resolution

With namespaced format\_ids, conflicts **cannot occur** - each domain controls its own namespace.

**No conflict:**

```json theme={null}
// Two different formats, both valid
{
  "format_id": {
    "agent_url": "https://publisher-a.com",
    "id": "video_30s"
  }
}
{
  "format_id": {
    "agent_url": "https://publisher-b.com",
    "id": "video_30s"
  }
}
```

If a buyer encounters the same namespaced format\_id from multiple sources, they are **the same format** - the namespace guarantees identity.

### Validation Rules

1. **Domain MUST match agent\_url domain:**
   ```json theme={null}
   // ✅ Valid - domain matches
   {
     "format_id": {
       "agent_url": "https://youragent.com",
       "id": "format_x"
     }
   }

   // ❌ Invalid - domain mismatch
   {
     "format_id": {
       "agent_url": "https://otheragent.com",
       "id": "format_x"
     }
   }
   ```

2. **Domain MUST have valid agent card:**
   * Agent card must exist at `{domain}/.well-known/adagents.json`
   * Must declare MCP and/or A2A endpoints
   * Endpoints must be functional

3. **Format\_id MUST follow pattern:**
   * `{domain}:{format_id}` structure
   * Domain is valid DNS hostname
   * Format\_id is alphanumeric with underscores/hyphens

### Migration from Unnamespaced IDs

If you previously used simple IDs like `display_300x250`, migrate to namespaced versions:

**Before:**

```json theme={null}
{
  "format_id": {
    "agent_url": "https://youragent.com",
    "id": "display_300x250_old"
  }
}
```

**After:**

```json theme={null}
{
  "format_id": {
    "agent_url": "https://youragent.com",
    "id": "display_300x250"
  }
}
```

Support both during transition if needed, but new implementations should use namespaced IDs from the start.

## Reference Agent as Format Authority

Each format includes a `format_id` field with an `agent_url` indicating its authoritative source:

```json theme={null}
{
  "$schema": "/schemas/3.0.0-rc.2/core/format.json",
  "format_id": {
    "agent_url": "https://creative.adcontextprotocol.org",
    "id": "display_300x250"
  },
  "name": "Medium Rectangle",
  "type": "display"
}
```

The creative agent at that URL is the definitive source for:

* Complete format specifications
* Asset requirements and validation rules
* Preview generation
* Rendering instructions

## When NOT to Use Standard Formats

Define your own formats when:

1. **Unique technical requirements** - Your platform needs different specs than IAB standards
2. **Custom validation** - You require additional creative review or approval
3. **Proprietary assembly** - Your rendering pipeline has special requirements
4. **Premium experiences** - Differentiated ad products not covered by standard formats

Even in these cases, you can reference standard formats for basic inventory while defining custom formats for premium placements.

## Implementation Notes

### Format Authority Pattern

The `agent_url` field enables a **distributed format authority** model:

* Reference agent is authoritative for IAB standards
* Each publisher is authoritative for their custom formats
* Buyers can discover and validate against the correct authority

### Version Management

The reference creative agent maintains format versions and compatibility:

* Format definitions evolve with industry standards
* Backward compatibility is maintained
* Buyers can rely on stable format\_id values

### What Makes a Format "Standard"

**Standard formats** are those defined by the reference creative agent at `https://creative.adcontextprotocol.org` based on:

1. **Industry specifications** - IAB standards, VAST/VPAID specs, common ad unit sizes
2. **Cross-platform compatibility** - Work across multiple publishers without customization
3. **Stable definitions** - Versioned and maintained for consistency across the ecosystem

**Protocol perspective:** At the protocol level, standard formats are just formats like any other - there's no special API treatment. The `agent_url` field identifies the reference agent as the authoritative source, just as it would for any custom format.

**Ecosystem perspective:** Standard formats enable portability. A buyer can build one creative and use it across many publishers who reference the same format definitions.

## Related Documentation

* [Creative Protocol Overview](/dist/docs/3.0.0-rc.2/creative) - How formats, manifests, and agents work together
* [Creative Formats](/dist/docs/3.0.0-rc.2/creative/formats) - Understanding format specifications and discovery
* [Channel Guides](/dist/docs/3.0.0-rc.2/creative/channels/video) - Detailed format documentation by media type
* [list\_creative\_formats Task](/dist/docs/3.0.0-rc.2/creative/task-reference/list_creative_formats) - API reference for format discovery