Understanding Authorization

Authorized properties in AdCP let buyers restrict campaigns to verified inventory using property lists and supply path validation.

One of the foundational challenges in digital advertising is unauthorized resale - ensuring that sales agents are actually authorized to represent the advertising properties they claim to sell. AdCP solves this problem through a comprehensive authorization system that builds on the lessons learned from ads.txt in programmatic advertising.

New to AdCP authorization? Read AdCP Basics: Authorized Properties for an accessible introduction to how authorization works in agentic advertising.

The Problem: Unauthorized Resale

Historical Context

In programmatic advertising, the Ads.txt initiative was created to solve a critical problem: unauthorized reselling of advertising inventory. Before ads.txt, bad actors could claim to represent popular websites and sell their inventory without permission, leading to:

• Revenue theft: Publishers lost money to unauthorized sellers
• Brand safety issues: Buyers couldn’t verify legitimate inventory sources
• Market fragmentation: No way to distinguish authorized from unauthorized sellers

The Same Problem in AI-Powered Advertising

AdCP faces similar challenges as AI agents begin to buy and sell advertising programmatically:

• AI sales agents may claim to represent properties they don’t actually control
• Buyer agents need to verify authorization before making purchases
• Publishers need a way to explicitly authorize specific sales agents
• Scale challenges: Manual verification doesn’t work for networks with thousands of properties

The Solution: AdCP Authorization System

AdCP prevents unauthorized resale through a three-part system:

1. Publisher Authorization: Publishers explicitly authorize sales agents via adagents.json with delegation_type (direct, delegated, or ad_network)
2. Operator Declaration: Operators declare their property portfolio in brand.json with the relationship field, using the same values as delegation_type
3. Agent Discovery: Sales agents declare their portfolio via get_adcp_capabilities in the media_buy.portfolio section

The first two create bilateral verification — like ads.txt + sellers.json in programmatic. Both sides must agree for the supply path to be trusted. See ad networks for the full pattern.

How Publishers Authorize Sales Agents

Publishers authorize sales agents by hosting an adagents.json file at /.well-known/adagents.json on their domain. This file lists all authorized agents and their permissions.

Example adagents.json

{
  "$schema": "https://adcontextprotocol.org/schemas/v3/adagents.json",
  "contact": {
    "name": "Sports Network Media",
    "email": "[e-mail]",
    "domain": "sportsnetwork.com"
  },
  "properties": [
    {
      "property_id": "sports_network_main",
      "property_type": "website",
      "name": "Sports Network",
      "identifiers": [
        {"type": "domain", "value": "sportsnetwork.com"}
      ],
      "tags": ["premium", "sports"]
    }
  ],
  "authorized_agents": [
    {
      "url": "https://sports-media-sales.com",
      "authorized_for": "All Sports Network properties",
      "authorization_type": "property_tags",
      "property_tags": ["sports"],
      "delegation_type": "direct"
    },
    {
      "url": "https://premium-ad-network.com",
      "authorized_for": "Premium inventory only",
      "authorization_type": "property_tags",
      "property_tags": ["premium"],
      "delegation_type": "ad_network",
      "countries": ["US", "CA"]
    }
  ],
  "last_updated": "2025-01-10T12:00:00Z"
}

Key Fields

• contact: Identifies the publisher/entity managing this file
• properties: Defines the properties covered by this authorization file
• authorized_agents: List of sales agents authorized to represent properties
  • url: Agent’s API endpoint URL
  • authorized_for: Human-readable description of authorization scope
  • authorization_type: How properties are selected (property_ids, property_tags, inline_properties, publisher_properties)
  • delegation_type: Whether this path is direct, delegated, or ad_network
  • collections: Optional collection selectors that narrow authorization to specific content programs
  • placement_ids: Optional placement IDs from the publisher’s placement registry in adagents.json
  • countries: Optional ISO 3166-1 alpha-2 country codes
  • effective_from / effective_until: Optional authorization window
  • exclusive: Whether this is the sole authorized path for the scoped inventory slice
• last_updated: ISO 8601 timestamp of last modification

How Sales Agents Share Authorized Properties

Sales agents use the get_adcp_capabilities task to declare their portfolio information in the media_buy.portfolio section. This serves multiple purposes:

1. Transparency: Buyers can see what publishers an agent represents
2. Validation enablement: Provides publisher domains for buyers to verify authorization via adagents.json
3. Portfolio overview: Includes primary channels, countries, and portfolio description

Property Declaration Example

{
  "properties": [
    {
      "property_type": "website",
      "name": "Sports Network",
      "identifiers": [
        {"type": "domain", "value": "sportsnetwork.com"}
      ],
      "tags": ["sports_network", "premium"],
      "publisher_domain": "sportsnetwork.com"
    },
    {
      "property_type": "radio",
      "name": "WXYZ-FM Chicago",
      "identifiers": [
        {"type": "station_id", "value": "WXYZ-FM"},
        {"type": "facility_id", "value": "fcc:21242"}
      ],
      "tags": ["local_radio", "midwest", "chicago"],
      "publisher_domain": "radionetwork.com"
    }
  ],
  "tags": {
    "sports_network": {
      "name": "Sports Network Properties",
      "description": "145 sports properties and networks"
    },
    "local_radio": {
      "name": "Local Radio Stations",
      "description": "1847 local radio stations across US markets"
    }
  },
  "advertising_policies": "We maintain strict brand safety standards. Prohibited categories include: tobacco and vaping products, online gambling and sports betting, cannabis and CBD products, political advertising, and speculative financial products (crypto, NFTs, penny stocks).\n\nWe also prohibit misleading tactics such as clickbait headlines, false scarcity claims, hidden pricing, and ads targeting vulnerable populations.\n\nCompetitor brands in the streaming media space are blocked by policy.\n\nFull advertising guidelines: https://publisher.com/advertising-policies"
}

Property Tags for Scale

For large networks representing thousands of properties, AdCP supports property tags to make the system manageable:

• Products can reference ["local_radio", "midwest"] instead of listing hundreds of stations
• Buyers use get_adcp_capabilities to discover the agent’s portfolio and validate authorization
• Authorization validation works on the resolved properties via adagents.json

Authorization Validation Workflow

Here’s how a buyer agent validates that a sales agent is authorized to represent claimed properties:

1. One-Time Setup

// Get portfolio information from capabilities
const capabilities = await salesAgent.call('get_adcp_capabilities');
const portfolio = capabilities.media_buy?.portfolio;
const publisherDomains = portfolio?.publisher_domains || [];

// For each publisher domain, fetch and cache adagents.json
const authorizationCache = {};

for (const domain of publisherDomains) {
  try {
    const adagents = await fetch(`https://${domain}/.well-known/adagents.json`);
    authorizationCache[domain] = await adagents.json();
  } catch (error) {
    console.warn(`Could not verify authorization for ${domain}`);
    authorizationCache[domain] = null;
  }
}

2. Product Validation

// When evaluating a product
const result = await salesAgent.call('get_products', {brief: "Chicago radio ads"});
const product = result.products[0];

// Validate authorization for each publisher in publisher_properties
const authorized = product.publisher_properties.every(pubProp => {
  const domain = pubProp.publisher_domain;
  const adagents = authorizationCache[domain];

  if (!adagents) return false; // No adagents.json found

  // Verify the sales agent is in publisher's authorized_agents
  return adagents.authorized_agents.some(agent =>
    agent.url === salesAgent.url &&
    isAuthorizedForProperties(agent, pubProp)
  );
});

if (!authorized) {
  throw new Error("Sales agent not authorized for claimed properties");
}

3. Ongoing Validation

• Cache adagents.json responses with reasonable TTL (e.g., 24 hours)
• Re-validate periodically for long-running campaigns
• Handle authorization changes gracefully (pause vs. reject)

Benefits of This Approach

For Publishers

• Explicit control over who can sell their inventory
• Granular permissions by property, collection, country, and date range
• Standard web hosting - no special infrastructure required
• Audit trail of authorized agents

For Sales Agents

• Clear authorization proof that buyers can verify
• Efficient tag-based grouping for large property portfolios
• Standardized declaration across all AdCP interactions

For Buyer Agents

• Automated verification of seller authorization
• Fraud prevention through cryptographic verification
• Confidence in purchases from verified inventory sources
• Scalable validation for large-scale automated buying

Security Considerations

Domain Verification

• HTTPS required: adagents.json must be served over HTTPS
• Domain ownership: Only domain owners can authorize agents for their properties
• Regular validation: Buyers should re-check authorization periodically

Authorization Scope

• Least privilege: Grant minimal necessary permissions
• Time bounds: Use start/end dates for temporary authorizations
• Property restrictions: Limit to specific paths or property types when appropriate

Error Handling

• Missing adagents.json: Treat as unauthorized (fail closed)
• Invalid JSON: Reject malformed authorization files
• Network errors: Implement retry logic with fallback policies
• Expired authorization: Handle gracefully in active campaigns

Integration with Product Discovery

Authorization validation integrates seamlessly with Product Discovery:

1. Discover products using get_products
2. Validate authorization for properties referenced in products
3. Proceed confidently with authorized inventory
4. Flag unauthorized products for manual review

This creates a trustworthy foundation for AI-powered advertising that prevents unauthorized resale while enabling efficient, automated transactions.

Technical Implementation

For complete technical details on implementing the adagents.json file format, including:

• File location and format requirements (/.well-known/adagents.json)
• JSON schema definitions and validation rules
• Mobile application and CTV implementation patterns
• Detailed property type specifications (website, mobile app, CTV, DOOH, podcast)
• Domain matching rules and wildcard patterns
• Validation code examples and error handling
• Security considerations and best practices

See the adagents.json Tech Spec for complete implementation guidance.

Related Documentation

• get_adcp_capabilities - Discover agent capabilities and portfolio information
• Product Discovery - How authorization integrates with product discovery
• Properties Schema - Technical property data model
• adagents.json Tech Spec - Complete adagents.json implementation guide