AdCP — adagents.json Tech Spec

The adagents.json file provides a standardized way for publishers to declare their properties and authorize sales agents. This is the foundation of Property Governance - it defines what properties exist and who can sell them.

Unified declaration model

adagents.json serves as the declaration mechanism for both property authorization and signal data provider registration. A single file at /.well-known/adagents.json can declare both properties and signals top-level fields simultaneously.

{
  "version": "1.0",
  "properties": [
    {
      "domain": "publisher.example.com",
      "agents": [
        { "agent_url": "https://ads.publisher.example.com", "relationship": "direct" }
      ]
    }
  ],
  "signals": [
    {
      "catalog_url": "https://signals.publisher.example.com/catalog.json",
      "relationship": "direct",
      "description": "First-party audience signals from publisher.example.com"
    }
  ]
}

This combined model is common for publishers with first-party data — the same domain authorizes sales agents (via properties) and declares signal catalogs (via signals). The two namespaces are independent: authorization for property sales does not grant signal access, and signal registration does not imply property authorization. See Signal data providers for the signals-side documentation.

AdAgents.json Builder - Validate existing files or create new ones with guided validation

Why `adagents.json` instead of `ads.txt`

ads.txt answers a narrower question: is this seller present on the publisher’s list, and is the relationship labeled DIRECT or RESELLER? That is useful, but it is too flat for many modern publisher sales models. It does not tell buyers:

which property is covered
which placements are covered
whether the path is direct, delegated, or network-mediated
whether the authorization is country-limited or time-bounded
whether a network-managed slot is the same thing as a publisher-managed premium placement

adagents.json is designed to carry that structure. It lets publishers declare property identity, placement identity, delegation type, scoped authorization, and publisher-defined grouping tags in one place.

Question	`ads.txt`	`adagents.json`
Is this seller declared at all?	Yes	Yes
Which property is covered?	No	Yes
Which placement is covered?	No	Yes
Can the publisher group inventory into governed buckets?	No	Yes, via `placement_tags`
Can authorization vary by country or time window?	No	Yes
Can the path be described as direct, delegated, or network-mediated?	Very weakly	Yes, via `delegation_type`

For the higher-level framing and a side-by-side example, see Why adagents.json is more expressive than ads.txt.

Where does sellers.json fit?

In programmatic, sellers.json is hosted by the seller/exchange and declares which publishers they represent. AdCP handles this through brand.json instead of a separate file. An operator declares properties in their brand.json using the relationship field, which uses the same values as delegation_type: direct, delegated, or ad_network. This creates the same bilateral verification pattern:

Programmatic	AdCP equivalent	Purpose
`ads.txt` (publisher)	`adagents.json` with `delegation_type` (publisher)	“These agents are authorized, here’s the relationship”
`sellers.json` (seller)	`brand.json` properties with `relationship` (operator)	“I sell for these publishers, here’s how”

Both sides must agree — and the delegation_type and relationship values should match. See ad networks for how this works in practice.

The field is called delegation_type in adagents.json and relationship in brand.json. The names differ because they describe the same commercial arrangement from different perspectives — the publisher delegates authority (delegation_type), the operator declares its relationship to the property (relationship). The values are the same: direct, delegated, ad_network.

File Location

Publishers must host the adagents.json file at:

https://example.com/.well-known/adagents.json

Following RFC 8615 well-known URI conventions, this location ensures consistent discoverability across publishers.

Basic Structure

The file must be valid JSON with UTF-8 encoding and return HTTP 200 status.

{
  "$schema": "https://adcontextprotocol.org/schemas/v3/adagents.json",
  "contact": {
    "name": "Example Publisher Ad Operations",
    "email": "adops@example.com",
    "domain": "example.com",
    "seller_id": "pub-example-12345",
    "tag_id": "67890"
  },
  "properties": [
    {
      "property_id": "example_site",
      "property_type": "website",
      "name": "Example Site",
      "identifiers": [
        {"type": "domain", "value": "example.com"}
      ]
    }
  ],
  "authorized_agents": [
    {
      "url": "https://agent.example.com",
      "authorized_for": "Official sales agent",
      "authorization_type": "property_ids",
      "property_ids": ["example_site"],
      "delegation_type": "direct",
      "exclusive": true
    }
  ],
  "last_updated": "2025-01-10T12:00:00Z"
}

Schema Fields

$schema (optional): JSON Schema reference for validation contact (optional): Contact info for entity managing this file

name (required): Name of managing entity (may be publisher or third-party)
email (optional): Contact email for questions/issues
domain (optional): Primary domain of managing entity
seller_id (optional): Seller ID from IAB Tech Lab sellers.json
tag_id (optional): TAG Certified Against Fraud ID
privacy_policy_url (optional): URL to entity’s privacy policy for consumer consent flows

properties (optional): Array of properties covered by this file (canonical property definitions)

supported_channels (optional): Advertising channels this property supports (e.g., ["display", "olv", "social"]). See Media Channel Taxonomy.

collections (optional): Collections produced or distributed by this publisher

Products reference these via collections selectors with publisher_domain and collection_ids
Useful when authorization needs to be scoped to specific series, podcasts, streams, or recurring content programs

placements (optional): Canonical placement definitions for the properties in this file

Products SHOULD reuse these placement_id values when declaring placements
Reusing a registered placement_id means the product is referring to the same semantic placement, not inventing a different one with the same ID
Placement definitions can include tags for grouping, property_ids or property_tags for property linkage, and optional format_ids for canonical format support
Authorization entries can narrow scope to specific placement_ids
Authorization entries can also use placement_tags for governed placement groupings such as programmatic, direct_only, or managed_by_riverline
Useful for expressing distinctions like “available via this agent only for homepage native feed” or “only for pre-roll”

tags (optional): Tag metadata providing human-readable context and enabling efficient grouping placement_tags (optional): Metadata for publisher-defined placement tags

Provides human-readable definitions for placement tag values used in placements[*].tags and authorized_agents[*].placement_tags
These are publisher-local concepts, not a global taxonomy

authorized_agents (required): Array of authorized sales agents

url (required): Agent’s API endpoint URL
authorized_for (required): Human-readable authorization description
authorization_type (required): Discriminator naming which selector field carries the scope. One of property_ids, property_tags, inline_properties, publisher_properties (for properties) or signal_ids, signal_tags (for signal providers). The corresponding selector field must be present and non-empty — see Authorization Patterns below.
delegation_type (optional): Commercial relationship for this path: direct, delegated, or ad_network
collections (optional): Additional collection selectors that narrow authorization to specific content programs
placement_ids (optional): Placement IDs from the top-level placements array that narrow authorization to specific placements
placement_tags (optional): Publisher-defined placement tags that narrow authorization to governed placement groups
countries (optional): ISO 3166-1 alpha-2 country codes limiting where the authorization applies
effective_from / effective_until (optional): Time window for the authorization
exclusive (optional): Whether this is the publisher’s sole authorized path for the scoped inventory slice
signing_keys (optional): Publisher-attested public keys buyers can pin when verifying signed agent responses
last_updated (optional): ISO 8601 timestamp when this authorized_agents[] entry last changed. Independent of the file-level last_updated. Advisory — enables validators to skip unchanged entries on partial walks. See managed-networks security for the conditional-refresh protocol it enables.
Additional fields: Depends on authorization_type (see patterns below)

revoked_publisher_domains (optional, managed-network use): Top-level array of publisher domains explicitly removed from a managed network’s authoritative file. Each entry has publisher_domain, revoked_at (ISO 8601), and optional reason. Validators MUST treat any listed domain as no-longer-authorized regardless of where else it appears in the file. See Publisher revocation for the operational lifecycle and validator-side durability rule. last_updated (optional): ISO 8601 timestamp of last modification property_features (optional): Array of governance agents that provide data about properties in this file

url (required): Agent’s API endpoint URL (governance agent implementing property governance tasks)
name (required): Human-readable name of the vendor/agent
features (required): Array of feature IDs this agent provides (e.g., ["carbon_score", "mfa_score"])
publisher_id (optional): Publisher’s identifier at this agent (for lookup)

This field enables governance agent discovery - buyers can find which agents have compliance, sustainability, or quality data for properties without querying every possible agent.

URL Reference Pattern

For publishers with complex infrastructure or CDN distribution, adagents.json can reference an authoritative URL instead of containing the full structure inline.

When to Use URL References

CDN Distribution: Serve authorization data from a global CDN for better performance
Centralized Management: Single source of truth across multiple domains
Large Files: When authorization data is too large for inline embedding
Dynamic Updates: When authorization needs frequent updates without touching domain files

URL Reference Structure

{
  "$schema": "https://adcontextprotocol.org/schemas/v3/adagents.json",
  "authoritative_location": "https://cdn.example.com/adagents/v2/adagents.json",
  "last_updated": "2025-01-15T10:00:00Z"
}

Requirements

HTTPS Required: The authoritative_location must use HTTPS
No Nested References: The authoritative file cannot itself be a URL reference (prevents infinite loops)
Same Schema: The authoritative file must be a valid inline adagents.json structure
Single Hop: Only one level of URL indirection is allowed

For a complete guide to deploying this pattern across hundreds or thousands of domains, see Managed Network Deployment.

Discovery fallback: ads.txt `managerdomain`

This is a legacy compatibility fallback for existing ads.txt-era publisher-manager setups. For managed-network deployments in AdCP, the normative delegation pattern remains authoritative_location in the publisher’s own /.well-known/adagents.json pointer file. New deployments SHOULD use that pattern.

When https://{publisher}/.well-known/adagents.json returns 404, validators MAY attempt a compatibility fallback via https://{publisher}/ads.txt:

Read ads.txt and parse managerdomain entries.
- Accepted form: MANAGERDOMAIN=example.com (IAB directive form only).
- Key matching is case-insensitive (MANAGERDOMAIN, managerdomain, etc.).
If one or more eligible managerdomain entries remain, use the last eligible entry in file order and attempt https://{managerdomain}/.well-known/adagents.json.
If that manager file validates and explicitly scopes authorization to the source publisher domain, treat it as the discovered authorization source for this lookup.

Safety rules for this fallback

One hop only: maximum depth is exactly one (publisher -> managerdomain). Do not chain managerdomain lookups.
Cycle detection required: if managerdomain points to a visited domain, ignore it.
#noagents opt-out: if a managerdomain line has a trailing comment containing the token noagents (case-insensitive), clients MUST ignore that managerdomain for adagents discovery. Example: MANAGERDOMAIN=example.com #NOAGENTS.
Explicit publisher scoping required: a manager-hosted adagents.json MUST positively name the source publisher domain in a publisher_domain field that is reachable from at least one authorized_agents[] entry. “Reachable” means one of the following paths resolves to the source domain:
1. Per-agent paths. The agent entry directly carries the publisher domain under publisher_properties[].publisher_domain, inside publisher_properties[].publisher_domains[] (the compact managed-network form), or under collections[].publisher_domain.
2. Property-level paths. The agent entry references one or more top-level properties[] entries by ID (property_ids) or by tag (property_tags), and at least one resolved property carries a publisher_domain matching the source. This is the shape used in production by Mediavine and other managed networks where a property declares its publisher_domain once and many agents reference it indirectly.
What does not satisfy this rule: an inline_properties selector whose inline properties omit publisher_domain, or a top-level property_tags selector whose resolved top-level properties carry no matching publisher_domain. If no reachable publisher_domain field matches the source, fallback MUST fail closed. The attack this protects against is implicit scoping — authorization that does not name the publisher anywhere the manager has to type the domain. Indirection through properties[].publisher_domain is safe because the manager has positively spelled the publisher’s domain in the same manifest; the gate filters to properties whose publisher_domain matches the source before considering the reference.
No success by silence: if the manager lookup fails, treat the publisher as missing adagents.json (same as no fallback).

This fallback is a compatibility affordance for publisher-manager topologies and does not replace the canonical /.well-known/adagents.json location.

Example Use Case: Multi-Domain Publisher

A publisher with multiple domains can maintain one authoritative file: On each domain (https://domain1.com/.well-known/adagents.json, https://domain2.com/.well-known/adagents.json, etc.):

{
  "$schema": "https://adcontextprotocol.org/schemas/v3/adagents.json",
  "authoritative_location": "https://cdn.publisher.com/adagents/v2/adagents.json",
  "last_updated": "2025-01-15T10:00:00Z"
}

Authoritative file (https://cdn.publisher.com/adagents/v2/adagents.json):

{
  "$schema": "https://adcontextprotocol.org/schemas/v3/adagents.json",
  "contact": {
    "name": "Publisher Ad Operations",
    "email": "adops@publisher.com"
  },
  "properties": [
    {
      "property_id": "domain1_site",
      "property_type": "website",
      "name": "Domain 1",
      "identifiers": [{"type": "domain", "value": "domain1.com"}],
      "publisher_domain": "domain1.com"
    },
    {
      "property_id": "domain2_site",
      "property_type": "website",
      "name": "Domain 2",
      "identifiers": [{"type": "domain", "value": "domain2.com"}],
      "publisher_domain": "domain2.com"
    }
  ],
  "authorized_agents": [
    {
      "url": "https://sales-agent.publisher.com",
      "authorized_for": "All publisher properties",
      "authorization_type": "property_ids",
      "property_ids": ["domain1_site", "domain2_site"]
    }
  ],
  "last_updated": "2025-01-15T09:00:00Z"
}

Validation Behavior

When AdCP validators encounter a URL reference:

Fetch Reference: Retrieve the file at /.well-known/adagents.json
Detect Reference: Check for authoritative_location field
Validate URL: Ensure authoritative_location is HTTPS and valid
Fetch Authoritative: Retrieve content from authoritative_location
Prevent Loops: Reject if authoritative file is also a reference
Validate Structure: Validate the authoritative file as normal inline structure

Validators MUST apply the fetch semantics, change-detection, and rollback protection rules in Managed network security considerations. That section is the canonical source for blast-radius guidance on the authoritative_location pattern.

Caching Recommendations

Cache reference files for 24 hours minimum
Cache authoritative files separately with their own TTL
Use last_updated timestamp to detect when cache should be invalidated
Implement exponential backoff for failed fetches

Absolute cache caps and refresh floors for authoritative files live in Managed network security considerations — the requirements there take precedence over any Cache-Control on the origin.

Authorization Patterns

AdCP supports four authorization patterns, each optimized for different use cases:

Pattern 1: Property IDs (Direct References)

Best for: Specific, enumerable property lists. Direct and unambiguous. Structure:

{
  "properties": [
    {
      "property_id": "cnn_ctv_app",
      "property_type": "ctv_app",
      "name": "CNN CTV App",
      "identifiers": [
        {"type": "roku_store_id", "value": "12345"}
      ]
    }
  ],
  "authorized_agents": [
    {
      "url": "https://cnn-ctv-agent.com",
      "authorized_for": "CNN CTV properties",
      "authorization_type": "property_ids",
      "property_ids": ["cnn_ctv_app"]
    }
  ]
}

How it works: Agent is authorized for specific properties listed in property_ids array. The properties must be defined in the top-level properties array.

Pattern 2: Property Tags (Efficient Grouping)

Best for: Large networks where one tag can reference hundreds/thousands of properties. Provides grouping efficiency without listing every property ID. Key Insight: Tags are not just “human-readable metadata” - they’re a performance optimization. A publisher with 500 properties can use one tag to authorize all of them, rather than listing 500 property IDs. Structure:

{
  "properties": [
    {
      "property_id": "instagram",
      "property_type": "mobile_app",
      "name": "Instagram",
      "identifiers": [
        {"type": "ios_bundle", "value": "com.burbn.instagram"}
      ],
      "tags": ["meta_network", "social_media"]
    },
    {
      "property_id": "facebook",
      "property_type": "mobile_app",
      "name": "Facebook",
      "identifiers": [
        {"type": "ios_bundle", "value": "com.facebook.Facebook"}
      ],
      "tags": ["meta_network", "social_media"]
    }
  ],
  "tags": {
    "meta_network": {
      "name": "Meta Network",
      "description": "All Meta-owned properties - enables one tag to authorize entire network"
    }
  },
  "authorized_agents": [
    {
      "url": "https://meta-ads.com",
      "authorized_for": "All Meta properties",
      "authorization_type": "property_tags",
      "property_tags": ["meta_network"]
    }
  ]
}

How it works: Agent is authorized for all properties that have ANY of the listed tags. Properties are matched against the tags array in each property definition.

Pattern 3: Inline Properties

Best for: Small, specific property sets without top-level property declarations. Structure:

{
  "authorized_agents": [
    {
      "url": "https://agent.com",
      "authorized_for": "Specific inventory",
      "authorization_type": "inline_properties",
      "properties": [
        {
          "property_type": "website",
          "name": "Example Site",
          "identifiers": [
            {"type": "domain", "value": "example.com"}
          ]
        }
      ]
    }
  ]
}

How it works: Properties are defined directly within the agent authorization entry instead of the top-level properties array. Useful when each agent has unique property definitions.

Pattern 4: Publisher Property References

Best for: Third-party agents representing multiple publishers. Single source of truth for property definitions. Structure:

{
  "contact": {
    "name": "Third-Party CTV Network"
  },
  "authorized_agents": [
    {
      "url": "https://ctv-network.com/api",
      "authorized_for": "CTV inventory from multiple publishers",
      "authorization_type": "publisher_properties",
      "publisher_properties": [
        {
          "publisher_domain": "cnn.com",
          "selection_type": "by_tag",
          "property_tags": ["ctv"]
        },
        {
          "publisher_domain": "espn.com",
          "selection_type": "by_tag",
          "property_tags": ["ctv"]
        }
      ]
    }
  ]
}

How it works: Agent references properties from OTHER publishers’ adagents.json files. The publisher_domain points to the publisher, and selection_type determines how to resolve properties (by_id or by_tag). Compact form for managed networks (publisher_domains): when the same predicate applies to many publishers — the canonical managed-network shape — replace the singular publisher_domain with the plural publisher_domains array. Each publisher_properties[] entry takes exactly one of publisher_domain or publisher_domains; both are equivalent for resolution and both satisfy the managerdomain fallback safety rule for every listed domain. The compact form is available on selection_type: "all" and "by_tag" only. It is intentionally NOT available on selection_type: "by_id": property IDs are publisher-scoped, and fanning the same ID set across N publishers’ files would silently authorize whichever inventory happens to share an ID at each publisher. Use one publisher_properties[] entry per publisher when each publisher’s ID set differs. Validators MUST reject by_id selectors that include publisher_domains[]. Validators MUST reject any publisher_properties[] entry that includes both publisher_domain and publisher_domains, and MUST reject any entry that includes neither. Implementations MAY mix the two forms across entries — for example, use the compact form for the bulk of represented publishers and a singular-form entry for an outlier publisher with a different tag predicate.

{
  "contact": { "name": "Example Managed Network" },
  "authorized_agents": [{
    "url": "https://agent.network.example/api",
    "authorized_for": "Managed-network display inventory across represented publishers",
    "authorization_type": "publisher_properties",
    "publisher_properties": [
      {
        "publisher_domains": ["site1.example", "site2.example", "site3.example"],
        "selection_type": "by_tag",
        "property_tags": ["managed_network"]
      }
    ],
    "delegation_type": "ad_network"
  }]
}

The above is semantically identical to repeating the singular-form entry once per domain. Use it when every represented publisher tags inventory the same way (typical of WordPress/managed-network deployments); fall back to one entry per publisher only when the selector predicate genuinely differs. Fan-out resolution semantics. Each listed domain in publisher_domains[] is resolved independently and in parallel against that publisher’s adagents.json:

Resolution is consumer-side, not publish-side. The manager file MUST NOT inline copies of each represented publisher’s properties; consumers (validators, buyer agents indexing the file) fetch each listed publisher’s own adagents.json to resolve the selector predicate. The manager file is the authorization declaration; the per-publisher files are the property catalog.
If a listed publisher’s adagents.json is unreachable (404, 5xx, timeout, fails its own validation), the selector resolves to the empty set for that publisher only — the entry remains valid for all other listed publishers. Consumers MUST NOT treat a single unreachable publisher as poisoning the rest of the compact entry.
If a listed publisher’s adagents.json carries no properties matching the predicate (no entries with the named tag), the selector resolves to the empty set for that publisher. Same partial-resolution rule applies.
Resolution caching follows each publisher’s own cache policy on their adagents.json, independently. A consumer SHOULD NOT extend or shorten one publisher’s cache TTL based on observations of another publisher in the same compact entry.

Authorization Qualifiers

The four authorization_type patterns above answer which inventory an agent can sell. The optional qualifiers below answer how that inventory is being made available.

`delegation_type`

direct: The publisher treats this endpoint as a direct way to buy from them, even if a third party operates the software behind the scenes
delegated: The agent is authorized to sell on the publisher’s behalf
ad_network: The inventory is sold through a network/package sales path rather than as the publisher’s direct endpoint

`collections`

Use collections when authorization should only apply to inventory associated with specific content programs. This is especially useful for CTV, streaming, podcasting, and creator inventory where the same property can carry many collections with different commercial arrangements.

`placement_ids`

Use placement_ids to narrow authorization to canonical placements published in this same adagents.json. This is the field that lets a publisher say “this agent is authorized for MSN homepage native feed, but not for the entire property” or “this network can sell pre-roll but not host-read sponsorships.” Canonical placement definitions can also carry:

tags for grouping placements across properties and products
property_ids or property_tags to answer “what placements are on property X?” and “what properties is placement Y on?”
format_ids to answer “what formats does this placement support?” without relying entirely on product-local placement definitions

`placement_tags`

Use placement_tags when authorization should apply to a governed placement group rather than a hand-maintained list of placement IDs. This is useful for commercial access patterns such as:

programmatic
direct_only
publisher_managed
managed_by_taboola

Unlike freeform labels, these tags should be treated as part of the publisher’s placement governance model because authorization decisions depend on them. Define them in top-level placement_tags metadata the same way property tags are documented in top-level tags.

`signing_keys`

Use signing_keys when the publisher wants to pin the public keys an authorized agent is allowed to sign with. This avoids trusting key discovery from the agent domain alone.

These are publisher-attested trust anchors, not just convenience metadata
Buyers should verify signed agent responses against the pinned keys in adagents.json
If an agent domain is compromised, pinned keys prevent the attacker from silently swapping both the endpoint and its advertised keys

Publishers MUST populate signing_keys for any authorized agent whose delegated scopes include mutating operations — any AdCP task that writes state on behalf of the publisher. In the 3.x catalog this means the media-buy task set (create_media_buy, update_media_buy, sync_creatives, update_performance_index) and any future task flagged as mutating in the media-buy task reference. Read-only discovery tasks (get_products, get_signals, list_creative_formats) are out of scope for this requirement. Leaving signing_keys empty for a mutating-scope authorization reduces the trust chain to counterparty-controlled jwks_uri discovery and forfeits the publisher’s pin as a cross-check. Verifier requirement: if the publisher’s adagents.json entry for an agent contains signing_keys, the verifier MUST reject any signature whose keyid is not in that pinned set, regardless of jwks_uri contents. The pin is authoritative; the agent-hosted JWKS is advisory and MUST NOT override it. Key rotation and cache semantics. To keep the pin usable across rotations without opening a DoS-by-rotation window:

Verifiers SHOULD cache the pinned signing_keys for at most the Cache-Control max-age the publisher serves on adagents.json, defaulting to one hour when no directive is present. Longer caching risks rejecting a legitimate rotated key.
On encountering an unknown keyid, the verifier MUST force-refresh the publisher’s adagents.json (bypassing cache) before final rejection. This prevents a stale cache from locking out a legitimately rotated key.
Publishers MAY carry overlapping keys in signing_keys during a rotation window so verifiers can accept signatures produced under either the old or the new key. The pinned set is unordered: presence in the set is sufficient for acceptance. Operators SHOULD remove the retired key from the pin once they are confident no in-flight traffic is still signing with it (hours, not days).

Bootstrap scope. The pin protects against agent-domain compromise: if the agent domain is taken over, an attacker cannot silently swap both the endpoint and its advertised keys because the publisher’s pin still governs acceptance. It does not protect against publisher-domain compromise (an attacker who controls adagents.json can rewrite the pin itself). First-ever retrieval of adagents.json is TLS-trust-only; the R-1 root-of-trust / key-transparency work (tracked in specs/registry-change-feed.md §Feed-event content signing) is the track that will strengthen this boundary. A follow-up is tracked to promote signing_keys from optional to required at the schema level for mutating-scope authorizations; the prose requirement above is the normative floor until that schema change lands.

`countries`

Use ISO 3166-1 alpha-2 country codes to constrain authorization geographically. This avoids ambiguous regional shorthands such as “LATAM” or “EMEA” and gives buyer agents a precise machine-readable scope.

`effective_from` / `effective_until`

Use these fields for time-bounded rights such as seasonal exclusives, windowed syndication, or temporary delegated sales agreements.

`exclusive`

Set exclusive: true when this agent is the publisher’s sole authorized path for the scoped slice of inventory. Leave it absent or set it to false when multiple agents are authorized concurrently.

Example: Scoped Delegation

{
  "placement_tags": {
    "programmatic": {
      "name": "Programmatic",
      "description": "Placements available through programmatic sales paths"
    },
    "direct_only": {
      "name": "Direct only",
      "description": "Placements reserved for direct publisher sales"
    }
  },
  "collections": [
    {
      "collection_id": "signal_noise",
      "name": "Signal & Noise",
      "kind": "series"
    }
  ],
  "placements": [
    {
      "placement_id": "pre_roll",
      "name": "Pre-roll",
      "tags": ["audio", "pre_roll", "programmatic"],
      "property_ids": ["publisher_podcast"],
      "collection_ids": ["signal_noise"],
      "format_ids": [
        {"agent_url": "https://creative.example.com", "id": "audio_15s"}
      ]
    },
    {
      "placement_id": "host_read",
      "name": "Host-read Mid-roll",
      "tags": ["audio", "host_read", "premium", "direct_only"],
      "property_ids": ["publisher_podcast"],
      "collection_ids": ["signal_noise"],
      "format_ids": [
        {"agent_url": "https://creative.example.com", "id": "audio_60s"}
      ]
    }
  ],
  "authorized_agents": [
    {
      "url": "https://sales.publisher.example.com",
      "authorized_for": "Direct US and CA sales for Signal & Noise host reads",
      "authorization_type": "property_ids",
      "property_ids": ["publisher_podcast"],
      "collections": [
        {
          "publisher_domain": "publisher.example.com",
          "collection_ids": ["signal_noise"]
        }
      ],
      "placement_tags": ["direct_only"],
      "delegation_type": "direct",
      "countries": ["US", "CA"],
      "exclusive": true
    },
    {
      "url": "https://network.example.com",
      "authorized_for": "Open network distribution outside US and CA for pre-roll",
      "authorization_type": "property_ids",
      "property_ids": ["publisher_podcast"],
      "collections": [
        {
          "publisher_domain": "publisher.example.com",
          "collection_ids": ["signal_noise"]
        }
      ],
      "placement_tags": ["programmatic"],
      "delegation_type": "ad_network",
      "countries": ["GB", "AU", "NZ"]
    }
  ]
}

This lets a publisher say “buy host reads directly from us in some markets, but use a network path for pre-roll in others” without implying that every authorized path is equivalent. adagents.json now provides a canonical publisher-level placement registry. Products still declare their own placements, but they SHOULD reuse the publisher’s registered placement_id values when the placement is part of that registry. Reusing a placement ID means the product is inheriting that placement’s identity; the product can narrow format_ids, preserve or narrow placement tags, or add operational detail, but it should not redefine the placement into something incompatible.

Domain Matching Rules

For website properties with domain identifiers, AdCP follows web conventions:

Base Domain (`example.com`)

Matches domain plus standard web subdomains:

✅ example.com
✅ www.example.com (standard web)
✅ m.example.com (standard mobile)
❌ subdomain.example.com (requires explicit authorization)

Specific Subdomain (`subdomain.example.com`)

Matches only that exact subdomain:

✅ subdomain.example.com
❌ All other domains/subdomains

Wildcard (`*.example.com`)

Matches ALL subdomains but NOT base:

✅ Any subdomain
❌ example.com (base domain requires separate authorization)

Real-World Examples

Example 1: Meta Network (Tag-Based)

Large network using tags for grouping efficiency:

{
  "contact": {
    "name": "Meta Advertising Operations",
    "email": "adops@meta.com",
    "domain": "meta.com",
    "seller_id": "pub-meta-12345",
    "tag_id": "12345",
    "privacy_policy_url": "https://www.meta.com/privacy/policy"
  },
  "properties": [
    {
      "property_type": "mobile_app",
      "name": "Instagram",
      "identifiers": [
        {"type": "ios_bundle", "value": "com.burbn.instagram"},
        {"type": "android_package", "value": "com.instagram.android"}
      ],
      "tags": ["meta_network"],
      "publisher_domain": "instagram.com"
    },
    {
      "property_type": "mobile_app",
      "name": "Facebook",
      "identifiers": [
        {"type": "ios_bundle", "value": "com.facebook.Facebook"},
        {"type": "android_package", "value": "com.facebook.katana"}
      ],
      "tags": ["meta_network"],
      "publisher_domain": "facebook.com"
    },
    {
      "property_type": "mobile_app",
      "name": "WhatsApp",
      "identifiers": [
        {"type": "ios_bundle", "value": "net.whatsapp.WhatsApp"},
        {"type": "android_package", "value": "com.whatsapp"}
      ],
      "tags": ["meta_network"],
      "publisher_domain": "whatsapp.com"
    }
  ],
  "tags": {
    "meta_network": {
      "name": "Meta Network",
      "description": "All Meta-owned properties - one tag authorizes entire network efficiently"
    }
  },
  "authorized_agents": [
    {
      "url": "https://meta-ads.com",
      "authorized_for": "All Meta properties",
      "authorization_type": "property_tags",
      "property_tags": ["meta_network"]
    }
  ]
}

Why this works: One tag (meta_network) authorizes all properties without listing individual property IDs. As Meta adds properties, they just tag them - no need to update agent authorization.

Example 2: CNN (Channel Segmentation)

Different agents for different channels:

{
  "contact": {
    "name": "CNN Advertising Operations",
    "email": "adops@cnn.com",
    "domain": "cnn.com"
  },
  "properties": [
    {
      "property_id": "cnn_ctv_app",
      "property_type": "ctv_app",
      "name": "CNN CTV App",
      "identifiers": [
        {"type": "roku_store_id", "value": "12345"}
      ],
      "tags": ["ctv"]
    },
    {
      "property_id": "cnn_web_us",
      "property_type": "website",
      "name": "CNN.com US",
      "identifiers": [
        {"type": "domain", "value": "cnn.com"}
      ],
      "tags": ["web"]
    }
  ],
  "authorized_agents": [
    {
      "url": "https://cnn-ctv-agent.com",
      "authorized_for": "CNN CTV properties",
      "authorization_type": "property_ids",
      "property_ids": ["cnn_ctv_app"],
      "delegation_type": "direct",
      "exclusive": true
    },
    {
      "url": "https://cnn-web-agent.com",
      "authorized_for": "CNN web properties",
      "authorization_type": "property_ids",
      "property_ids": ["cnn_web_us"],
      "delegation_type": "delegated",
      "countries": ["US", "CA"]
    }
  ]
}

Example 3: Publisher with Governance Agent References

Publishers can declare which governance agents have data about their properties using property_features. This enables buyers to discover where to get sustainability, quality, and suitability data.

{
  "$schema": "https://adcontextprotocol.org/schemas/v3/adagents.json",
  "contact": {
    "name": "Premium News Publisher",
    "email": "adops@news.example.com",
    "domain": "news.example.com"
  },
  "properties": [
    {
      "property_id": "news_main",
      "property_type": "website",
      "name": "News Example",
      "identifiers": [
        {"type": "domain", "value": "news.example.com"}
      ],
      "tags": ["premium", "news"],
      "publisher_domain": "news.example.com"
    }
  ],
  "tags": {
    "premium": {
      "name": "Premium Properties",
      "description": "High-quality, brand-suitable properties"
    },
    "news": {
      "name": "News Properties",
      "description": "News and journalism content"
    }
  },
  "authorized_agents": [
    {
      "url": "https://sales.news.example.com",
      "authorized_for": "All news properties",
      "authorization_type": "property_tags",
      "property_tags": ["news"]
    }
  ],
  "property_features": [
    {
      "url": "https://api.sustainability-vendor.example",
      "name": "Sustainability Vendor",
      "features": ["carbon_score", "green_media_certified"],
      "publisher_id": "pub_news_12345"
    },
    {
      "url": "https://api.quality-vendor.example",
      "name": "Quality Vendor",
      "features": ["mfa_score", "ad_density", "page_speed"]
    },
    {
      "url": "https://api.suitability-vendor.example",
      "name": "Suitability Vendor",
      "features": ["content_category", "brand_risk_score", "sentiment"],
      "publisher_id": "suit_news_67890"
    }
  ],
  "last_updated": "2025-01-10T18:00:00Z"
}

Why this works:

Publishers declare relationships with governance agents upfront
Buyers discover governance agents by reading adagents.json (no need to query every possible agent)
The publisher_id field helps agents look up the publisher’s data efficiently
Feature IDs tell buyers what data types are available without querying

Governance Agent Discovery

The property_features field solves a key discovery problem: how does a buyer know which governance agents have data about a given property?

When to Use property_features

Scenario	Use property_features?
Publisher has carbon scoring from a sustainability vendor	✅ Yes
Publisher has MFA score measured by a quality vendor	✅ Yes
Publisher has content classification from a suitability vendor	✅ Yes
Publisher self-reports brand suitability	❌ No - use property tags
Sales agent provides quality data	❌ No - that’s agent capability

Vendor Extensions

Governance agents can include vendor-specific data in feature definitions via an ext block. See get_adcp_capabilities for details.

Fetching and Validating

Using the AdAgents.json Builder

The easiest way to validate or create an adagents.json file is using the AdAgents.json Builder web tool. It provides:

Domain validation (fetches and checks /.well-known/adagents.json)
Structure validation against the JSON schema
Agent card endpoint verification (checks if agent URLs respond correctly)
Guided file creation with proper formatting

Programmatic Validation

For programmatic validation, use the validation API:

// Validate a domain's adagents.json file
const response = await fetch('https://adcontextprotocol.org/api/adagents/validate', {
  method: 'POST',
  headers: { 'Content-Type': 'application/json' },
  body: JSON.stringify({ domain: 'example.com' })
});

const { success, data } = await response.json();

if (success && data.found) {
  console.log(`Valid: ${data.validation.valid}`);
  console.log(`Agents: ${data.validation.raw_data?.authorized_agents?.length || 0}`);

  // Check for any validation errors
  if (data.validation.errors?.length > 0) {
    console.log('Errors:', data.validation.errors.map(e => e.message));
  }
} else {
  console.log('No adagents.json found at this domain');
}

The validation API fetches https://{domain}/.well-known/adagents.json, validates its structure, follows URL references if present, and optionally checks agent card endpoints.

Using AdCP Client Libraries

The AdCP client libraries provide built-in validation and authorization checking:

import asyncio
from adcp import fetch_adagents, verify_agent_authorization

async def validate_authorization():
    # Fetch and validate adagents.json from a publisher domain
    adagents_data = await fetch_adagents('example-publisher.com')

    # Check if a specific agent is authorized
    is_authorized = verify_agent_authorization(
        adagents_data=adagents_data,
        agent_url='https://our-sales-agent.com',
        property_type='website',
        property_identifiers=[{'type': 'domain', 'value': 'example-publisher.com'}]
    )

    print(f"Agent authorized: {is_authorized}")
    print(f"Total agents: {len(adagents_data.get('authorized_agents', []))}")

asyncio.run(validate_authorization())

The Python library handles validation automatically when fetching - if the adagents.json file is malformed or missing required fields, it raises AdagentsValidationError.

Best Practices

1. Use Appropriate Authorization Pattern

Property IDs: Small, enumerable lists (< 20 properties)
Property Tags: Large networks (100+ properties)
Inline Properties: Simple cases without top-level properties
Publisher Properties: Third-party agents representing multiple publishers

2. Cache Files Appropriately

Cache for 24 hours minimum
Use last_updated timestamp to detect staleness
Handle 404 as “no file” (not an error - proceed without validation)
Implement retry logic with exponential backoff for network errors

3. Validate Structure

Validate against JSON schema before processing
Check required fields exist (authorized_agents array)
Verify authorization scope matches product claims
Cross-reference with seller.json if available

4. Handle Missing Files Gracefully

404 status = No file present (not an authorization failure)
Absence of file does not mean agent is unauthorized
Use adagents.json as verification, not requirement

5. Handle Per-Property Validation Failures Gracefully

File-level failures (unparseable JSON, missing required top-level authorized_agents) MUST abort processing for that domain — the file is unusable. Per-property validation failures are a separate tier: a single property object in an otherwise-valid file may omit identifiers or another required field due to a publisher-side templating error or a partial write. Per-property validation failures MUST NOT prevent processing of remaining properties in the same file. Treat a non-conforming property as absent from the array — never as a reason to abort the run:

Skip the non-conforming property
Log a warning including the source domain, the property’s index in the array, and the reason (e.g., missing required field: identifiers)
Continue processing all remaining properties in the file

Aborting the full crawl on a per-property failure is a common implementation error. A single malformed property in a managed-network file that covers hundreds of publisher domains can silently zero out an entire discovery run, making this failure mode disproportionately disruptive relative to the size of the underlying data problem. This follows the same principle as IAB Tech Lab ads.txt 1.1 §3.1, which specifies that a malformed line MUST be ignored and processing of subsequent lines MUST continue. This applies to all surfaces where property objects appear: the top-level properties array, inline properties inside authorized_agents[*].properties (the inline_properties authorization type), and properties fetched and resolved from remote domains during publisher_properties resolution.

Next Steps

After implementing adagents.json validation:

Integrate with Product Discovery: Use get_products to discover inventory
Validate at Purchase: Check authorization before calling create_media_buy
Cache Property Mappings: Store resolved properties for efficient validation
Monitor Authorization: Track validation success rates and unauthorized attempts

Learn More

AdCP Basics: Authorized Properties - Accessible introduction to AdCP authorization
get_adcp_capabilities - Discover agent capabilities and portfolio
Property Schema - Property definition structure
AdAgents.json Builder - Web-based validator and creator

Documentation

Documentation Index

​Unified declaration model

​Why adagents.json instead of ads.txt

​Where does sellers.json fit?

​File Location

​Basic Structure

​Schema Fields

​URL Reference Pattern

​When to Use URL References

​URL Reference Structure

​Requirements

​Discovery fallback: ads.txt managerdomain

​Safety rules for this fallback

​Example Use Case: Multi-Domain Publisher

​Validation Behavior

​Caching Recommendations

​Authorization Patterns

​Pattern 1: Property IDs (Direct References)

​Pattern 2: Property Tags (Efficient Grouping)

​Pattern 3: Inline Properties

​Pattern 4: Publisher Property References

​Authorization Qualifiers

​delegation_type

​collections

​placement_ids

​placement_tags

​signing_keys

​countries

​effective_from / effective_until

​exclusive

​Example: Scoped Delegation

​Domain Matching Rules

​Base Domain (example.com)

​Specific Subdomain (subdomain.example.com)

​Wildcard (*.example.com)

​Real-World Examples

​Example 1: Meta Network (Tag-Based)

​Example 2: CNN (Channel Segmentation)

​Example 3: Publisher with Governance Agent References

​Governance Agent Discovery

​When to Use property_features

​Vendor Extensions

​Fetching and Validating

​Using the AdAgents.json Builder

​Programmatic Validation

​Using AdCP Client Libraries

​Best Practices

​1. Use Appropriate Authorization Pattern

​2. Cache Files Appropriately

​3. Validate Structure

​4. Handle Missing Files Gracefully

​5. Handle Per-Property Validation Failures Gracefully

​Next Steps

​Learn More

Unified declaration model

Why `adagents.json` instead of `ads.txt`

Where does sellers.json fit?

File Location

Basic Structure

Schema Fields

URL Reference Pattern

When to Use URL References

URL Reference Structure

Requirements

Discovery fallback: ads.txt `managerdomain`

Safety rules for this fallback

Example Use Case: Multi-Domain Publisher

Validation Behavior

Caching Recommendations

Authorization Patterns

Pattern 1: Property IDs (Direct References)

Pattern 2: Property Tags (Efficient Grouping)

Pattern 3: Inline Properties

Pattern 4: Publisher Property References

Authorization Qualifiers

`delegation_type`

`collections`

`placement_ids`

`placement_tags`

`signing_keys`

`countries`

`effective_from` / `effective_until`

`exclusive`

Example: Scoped Delegation

Domain Matching Rules

Base Domain (`example.com`)

Specific Subdomain (`subdomain.example.com`)

Wildcard (`*.example.com`)

Real-World Examples

Example 1: Meta Network (Tag-Based)

Example 2: CNN (Channel Segmentation)

Example 3: Publisher with Governance Agent References

Governance Agent Discovery

When to Use property_features

Vendor Extensions

Fetching and Validating

Using the AdAgents.json Builder

Programmatic Validation

Using AdCP Client Libraries

Best Practices

1. Use Appropriate Authorization Pattern

2. Cache Files Appropriately

3. Validate Structure

4. Handle Missing Files Gracefully

5. Handle Per-Property Validation Failures Gracefully

Next Steps

Learn More