Sponsored Intelligence Specification

Formal AdCP Sponsored Intelligence specification. Session states, transport requirements, capability negotiation, standard UI components, identity and consent rules, commerce integration, and conformance criteria.

Experimental. Sponsored Intelligence is part of AdCP 3.0 as an experimental surface (feature id sponsored_intelligence.core) — the protocol surface (session lifecycle, UI components, identity/consent object shape, and capability negotiation) may change between 3.x releases with at least 6 weeks’ notice. Sellers implementing SI MUST declare sponsored_intelligence.core in experimental_features. See experimental status for the full contract and the 3.1.0 roadmap for planned changes.

This document defines the Sponsored Intelligence (SI) Protocol specification. The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL” in this document are to be interpreted as described in RFC 2119.

Protocol Overview

The SI Protocol defines how AI assistants (hosts) invoke and interact with brand agent endpoints to enable conversational brand experiences. The protocol consists of:

1. Discovery - How hosts discover brand agents and their capabilities
2. Offering Lookup - Anonymous pre-flight checks before session handoff
3. Session Management - Initiation, messaging, and termination
4. Capability Negotiation - Determining supported features
5. UI Components - Standard visual elements for rendering

Transport Requirements

Supported Transports

Brand agents MUST support at least one of the following transports:

Transport	Protocol	Description
MCP	Model Context Protocol	Tool-based interaction via JSON-RPC
A2A	Agent-to-Agent	Message-based interaction

Brand agents SHOULD support MCP as the preferred transport.

Transport Declaration

Brand agents declare supported transports via get_adcp_capabilities:

{
  "adcp": { "major_versions": [2] },
  "supported_protocols": ["sponsored_intelligence"],
  "sponsored_intelligence": {
    "endpoint": {
      "transports": [
        { "type": "mcp", "url": "https://brand.example/mcp" }
      ],
      "preferred": "mcp"
    },
    "capabilities": { ... },
    "brand": { "domain": "brand.example" }
  }
}

If multiple transports are declared, the response SHOULD include a preferred field.

Discovery

Capability Discovery

Brand agents MUST implement the get_adcp_capabilities task to declare SI support. When a host calls this task, the response MUST include:

• sponsored_intelligence in the supported_protocols array
• A sponsored_intelligence object containing:
  • endpoint - Transport configuration (REQUIRED)
  • capabilities - Supported modalities and components (REQUIRED)

The response SHOULD include:

• brand - Brand reference (domain-based identity)

Get Offering

Purpose

The si_get_offering task retrieves offering details and availability before session handoff. This allows hosts to show offering information (pricing, product availability) to users before asking for consent to engage with the brand.

Requirements

Hosts MAY call si_get_offering before initiating a session.

If a host calls si_get_offering:

1. The request MUST NOT include user PII
2. The request MUST include offering_id
3. The request MAY include intent for personalized results (e.g., “mens size 14 near Cincinnati”)
4. The request MAY set include_products: true to get matching products
5. Brand agents MUST return an offering_token if available
6. Brand agents SHOULD return a ttl_seconds indicating validity duration

Offering Token Flow

If a host receives an offering_token:

1. The host SHOULD include this token in the subsequent si_initiate_session request
2. The brand agent MAY use the token to correlate offering lookups with sessions
3. The token MUST be treated as opaque by the host

{
  "offering_token": "offering_abc123xyz"
}

Matching Products

When include_products is true and intent is provided, the response MAY include matching products:

{
  "available": true,
  "offering_token": "offering_abc123xyz",
  "offering": {
    "title": "Nike Summer Sale",
    "summary": "Up to 50% off summer collection",
    "price_hint": "from $89"
  },
  "matching_products": [
    {
      "product_id": "nike-air-max-90",
      "name": "Nike Air Max 90",
      "price": "$129",
      "availability_summary": "Size 14 in stock"
    }
  ],
  "total_matching": 12
}

This enables hosts to show rich previews before session initiation.

Session Lifecycle

Session States

Schema: enums/si-session-status.json

SI sessions progress through the following states. Terminal states (complete, terminated) allow no further messages.

State	Description
active	Session is in progress and accepting messages
pending_handoff	Brand agent is requesting handoff to a commerce or external flow
complete	Session ended normally after successful conversation or handoff
terminated	Session was ended due to timeout, error, policy violation, or explicit host/user action

Session State Transitions

si_initiate_session ──▶ active
                         │
                         ├── si_send_message ──▶ pending_handoff
                         │                           │
                         │                           └── si_terminate_session ──▶ complete (terminal)
                         │                               (handoff_transaction
                         │                                or handoff_complete)
                         │
                         ├── si_send_message ──▶ complete (terminal)
                         │   (conversation concluded)
                         │
                         └── si_terminate_session ──▶ terminated (terminal)
                             (user_exit, session_timeout,
                              or host_terminated)

Any non-terminal ── si_terminate_session(user_exit/timeout/host) ──▶ terminated

Rules:

• Brand agents MUST return session_status: "active" from si_initiate_session on success
• Brand agents MUST return session_status on every si_send_message response
• When session_status is pending_handoff, the response MUST include a handoff object
• Brand agents MAY transition from active to pending_handoff on any si_send_message response when the conversation reaches a commerce or checkout intent
• Brand agents MAY transition from active directly to complete on a si_send_message response when the conversation has concluded (e.g., question answered, no further action needed)
• Hosts MUST call si_terminate_session to end a session. Brand agents MUST accept termination from any non-terminal state.
• Brand agents MUST return SESSION_NOT_FOUND for messages sent to an unknown or expired session
• Brand agents MUST return SESSION_TERMINATED for messages sent to a session in complete or terminated state. Brand agents that prioritize minimizing information disclosure MAY return SESSION_NOT_FOUND for terminated sessions as well — the recovery path is identical in both cases.
• Terminal states are irreversible — once a session is complete or terminated, a new session must be initiated

Session Timeout

Sessions SHOULD have a maximum inactivity timeout. Brand agents MAY enforce timeout by transitioning idle sessions to terminated.

• Brand agents SHOULD treat sessions as expired after a period of inactivity (RECOMMENDED: 5 minutes for conversational sessions)
• Brand agents SHOULD return SESSION_NOT_FOUND for messages sent to an expired session, rather than silently creating a new session
• Hosts SHOULD track last_active_at and warn users before session timeout when possible
• Brand agents MAY include session_ttl_seconds in the si_initiate_session response to communicate the timeout duration to the host

Initiate Session

The si_initiate_session task establishes a new SI session.

Request Requirements

Hosts MUST include:

• intent - Natural language description of user intent — the conversation handoff from host to brand agent
• identity - User identity with consent status

Hosts SHOULD include:

• supported_capabilities - Host’s capability set for negotiation
• offering_token - Token from si_get_offering if performed

Hosts MAY include:

• media_buy_id - AdCP media buy ID if triggered by advertising
• offering_id - Brand-specific offering to apply
• placement - Where this session was triggered

Response Requirements

Brand agents MUST return:

• session_id - Unique identifier for this session

Brand agents SHOULD return:

• response.message - Initial conversational message
• negotiated_capabilities - Intersection of brand and host capabilities

Send Message

The si_send_message task exchanges messages within an active session.

Request Requirements

Hosts MUST include:

• session_id - Active session identifier

Hosts MUST include one of:

• message - User’s text message
• action_response - Response to a UI action

Response Requirements

Brand agents MUST return:

• session_id - The session identifier
• session_status - Current session state (active, pending_handoff, or complete)

Brand agents SHOULD return:

• response.message - Conversational response

If session_status is pending_handoff, the response MUST include:

• handoff - Handoff configuration for commerce flow

Terminate Session

The si_terminate_session task ends an SI session.

Request Requirements

Hosts MUST include:

• session_id - Session to terminate
• reason - Termination reason

Termination Reasons

Reason	Resulting State	Description
handoff_transaction	complete	User proceeding to purchase; brand agent SHOULD return acp_handoff data
handoff_complete	complete	Conversation completed successfully
user_exit	terminated	User ended the session
session_timeout	terminated	Session timed out due to inactivity
host_terminated	terminated	Host ended the session (policy/error)

Handoff Data

When reason is handoff_transaction, the brand agent SHOULD return an acp_handoff object in the termination response:

Field	Type	Description
checkout_url	uri	Brand’s ACP checkout endpoint. Hosts MUST validate this is HTTPS before opening (see Security Considerations).
checkout_token	string	Opaque token to pass to the checkout endpoint. Correlates the SI session with the transaction.
payload	object	Rich checkout context (product details, applied offers, pricing). Alternative to checkout_token for integrations that need structured data.
expires_at	datetime	When this handoff data expires. Hosts SHOULD initiate checkout before this time.

Brand agents SHOULD include either checkout_token or payload (or both) so the host can pass session context to the checkout endpoint.

Brand agents MAY also return a follow_up object with post-session context (e.g., summary of what was discussed, next steps).

Capability Negotiation

Negotiation Process

1. Brand declares capabilities in SI manifest
2. Host sends supported capabilities in session initiation
3. Brand returns negotiated (intersection) capabilities in response
4. Session uses only negotiated capabilities

Capability Categories

Modalities

Modalities define interaction modes:

Modality	Description	Required Support
conversational	Text exchange	REQUIRED for all implementations
voice	Audio-based interaction	OPTIONAL
video	Video content playback	OPTIONAL
avatar	Animated video presence	OPTIONAL

All SI implementations MUST support conversational modality.

Standard Components

The following components MUST be renderable by all compliant hosts:

Component	Purpose
text	Conversational message
link	URL with label
image	Single image
product_card	Product display with CTA
carousel	Array of cards/images
action_button	CTA that triggers callback

Extension Components

Hosts MAY support additional components:

Component	Purpose
app_handoff	Platform-specific app handoff
integration_actions	MCP/A2A installation prompts

Brand agents MUST NOT rely on extension components for core functionality.

UI Element Requirements

Standard Component Data

Each standard component MUST include the required fields as defined in si-ui-element.json:

text: message (required)

link: url, label (required); preview (optional)

image: url, alt (required); caption (optional)

product_card: title, price (required); subtitle, image_url, description, badge, cta (optional)

carousel: items (required); title (optional)

action_button: label, action (required); payload (optional)

Action Handling

When a user interacts with an action_button:

1. The host MUST send an action_response via si_send_message
2. The action_response MUST include the action identifier
3. The action_response SHOULD include the payload if provided

Integration Actions

The integration_actions component allows brand agents to offer persistent connections:

{
  "type": "integration_actions",
  "data": {
    "actions": [
      { "type": "mcp", "label": "Add as MCP Tool", "highlighted": true },
      { "type": "a2a", "label": "Connect via A2A" }
    ]
  }
}

Hosts MAY render integration actions if they support the integration type.

Identity and Privacy

Consent Requirements

Hosts MUST obtain explicit user consent before sharing identity with brand agents.

The consent flow MUST:

1. Clearly identify what data will be shared
2. Reference the brand’s privacy policy
3. Allow the user to decline

Identity Object

When consent is granted, the identity object MUST include:

• consent_granted: true
• consent_timestamp - When consent was obtained
• consent_scope - Array of data types consented to
• privacy_policy_acknowledged.brand_policy_url

The user object MAY include:

• email
• name
• locale
• shipping_address

Anonymous Sessions

If consent is not granted:

• identity.consent_granted MUST be false
• identity.anonymous_session_id SHOULD be provided
• No PII MUST be transmitted

Commerce Integration

ACP Handoff

When session_status is pending_handoff with handoff.type: "transaction":

1. The host SHOULD initiate ACP checkout flow
2. The handoff.intent MUST describe the purchase intent
3. The handoff.context_for_checkout MAY include conversation context

Commerce Actions

The action_button component MAY include commerce actions:

Action	Description
acp_checkout	Initiate ACP checkout
add_to_cart	Add item to persistent cart

Error Handling

Error Response

Brand agents MUST return errors in the errors array using the standard error schema:

{
  "errors": [
    {
      "code": "SESSION_NOT_FOUND",
      "message": "Session has expired or does not exist"
    }
  ]
}

Error Codes

SI uses both standard AdCP error codes and SI-specific codes:

Standard AdCP error codes (from enums/error-code.json):

Code	Description
SESSION_NOT_FOUND	Session ID is invalid, expired, or does not exist
SESSION_TERMINATED	Session has been terminated and cannot accept further messages
REFERENCE_NOT_FOUND	Generic fallback when the referenced SI offering, proposal, or other resource does not exist or is not accessible. Returned uniformly for both cases — see Uniform response for inaccessible references
RATE_LIMITED	Too many requests
SERVICE_UNAVAILABLE	Brand agent is temporarily unavailable

SI-specific codes (brand agents MAY return these for SI-specific errors):

Code	Description
offer_unavailable	Referenced offer is no longer available
capability_unsupported	Required capability not available

Security Considerations

Transport Security

All SI communications MUST use HTTPS with TLS 1.2 or higher.

Token Security

• Availability tokens MUST be opaque and unpredictable
• Session IDs MUST be unique and unpredictable
• Tokens SHOULD expire within a reasonable timeframe

Handoff URL Validation

Hosts MUST validate checkout_url in acp_handoff data before presenting it to users. Hosts SHOULD restrict to https scheme and MAY verify the domain matches the brand agent’s registered domain. Hosts MUST NOT open javascript:, data:, or other non-HTTPS URIs from handoff data.

Data Minimization

• Hosts MUST NOT send PII without consent
• Brand agents SHOULD minimize data collection
• Session data SHOULD be deleted after termination

Conformance

Host Conformance

A conformant SI host MUST:

1. Support MCP transport
2. Render all standard components
3. Implement session lifecycle (initiate, send, terminate)
4. Obtain consent before sharing identity
5. Support capability negotiation

Brand Agent Conformance

A conformant SI brand agent MUST:

1. Publish an SI manifest
2. Support at least one specified transport
3. Support conversational modality
4. Return valid session IDs
5. Handle all termination reasons

Version History

Version	Date	Changes
1.0.0	2025-01	Initial specification