si_initiate_session

si_initiate_session is the AdCP task that starts a Sponsored Intelligence session. Pass user intent, consented identity, and host capabilities to a brand agent and receive a personalized response.

Experimental. Sponsored Intelligence (si_get_offering, si_initiate_session, si_send_message, si_terminate_session) is part of AdCP 3.0 as an experimental surface — it may change between 3.x releases with at least 6 weeks’ notice. Sellers implementing any of these tasks MUST declare sponsored_intelligence.core in experimental_features. See experimental status for the full contract.

Start a conversational session with a brand agent. The host platform invokes this task when a user expresses interest in engaging with a brand.

Request

Field	Type	Required	Description
intent	string	Yes	Natural language description of user intent — the conversation handoff from the host
identity	object	Yes	User identity with consent status
media_buy_id	string	No	AdCP media buy ID if triggered by advertising
placement	string	No	Where the session was triggered (e.g., “chatgpt_search”)
offering_id	string	No	Brand-specific offering reference to apply
supported_capabilities	object	No	What the host platform supports
offering_token	string	No	Token from si_get_offering for correlation
sponsored_context_receipt	object	No	Host receipt for sponsored context accepted before session initiation
context	object	No	Opaque correlation data echoed unchanged in the response (see application context)

Offering Token

If a host performed a si_get_offering lookup before initiating, include the token for session continuity:

{
  "offering_token": "offering_abc123xyz"
}

The token lets the brand agent know exactly what products were shown to the user (and in what order). This enables natural conversation flow:

• User sees: “Nike Pegasus ($89), Air Max ($129), Vomero ($139)”
• User says: “Tell me more about the middle one”
• Brand agent resolves “middle one” → Air Max via the token’s stored context

Sponsored Context Receipt

If the host accepted or explicitly rejected sponsored context from a pre-session lookup, include sponsored_context_receipt to make the host’s boundary decision visible to the brand/seller:

{
  "offering_token": "offering_abc123xyz",
  "sponsored_context_receipt": {
    "sponsored_context": {
      "paying_principal": {
        "brand": { "domain": "acme-running.example" },
        "display_name": "Acme Running"
      },
      "context_use": "comparison_set",
      "disclosure_obligation": {
        "required": true,
        "label_text": "Sponsored results from Acme Running"
      }
    },
    "host_receipt": {
      "status": "accepted",
      "accepted_context_use": "comparison_set",
      "received_at": "2025-01-19T10:00:02Z",
      "host_surface": "assistant_comparison",
      "disclosure_commitment": {
        "status": "accepted",
        "label_text": "Sponsored results from Acme Running"
      }
    }
  }
}

The receipt records whether the host accepted or rejected the sponsored context. For accepted receipts, it records what the host committed to honor. It does not assert that AdCP can inspect hidden model reasoning.

Receipt field	Description
sponsored_context	Sender declaration being acknowledged: paying principal, declared use mode, and disclosure obligation
host_receipt.status	accepted when the host honored the declaration; rejected when it did not use the context
host_receipt.accepted_context_use	Required for accepted receipts; must match the declaration’s context_use
host_receipt.disclosure_commitment	Required for accepted receipts; records the host’s disclosure commitment
host_receipt.rejection_reason	Optional explanation when the host rejects the sponsored context

An accepted receipt cannot down-scope the use mode or decline a required disclosure. A host that cannot honor either condition rejects the sponsored context instead. Rejected receipts must omit accepted_context_use and disclosure_commitment.

Identity Object

When consent_granted is true:

Field	Type	Required	Description
consent_granted	boolean	Yes	Must be true
consent_timestamp	string	Yes	ISO 8601 timestamp of consent
consent_scope	array	Yes	Fields the user agreed to share
privacy_policy_acknowledged	object	No	Brand policy user accepted
user	object	Yes	User’s PII

When consent_granted is false:

Field	Type	Required	Description
consent_granted	boolean	Yes	Must be false
anonymous_session_id	string	Yes	Unique ID for this anonymous session

Supported Capabilities Object

Declares what the host platform can render:

{
  "modalities": {
    "conversational": true,
    "voice": { "providers": ["elevenlabs", "openai"] },
    "video": false,
    "avatar": false
  },
  "components": {
    "standard": ["text", "link", "image", "product_card", "carousel", "action_button"],
    "extensions": {
      "chatgpt_apps_sdk": "1.0"
    }
  },
  "commerce": {
    "acp_checkout": true
  }
}

Response

Field	Type	Description
session_id	string	Unique identifier for this session
response	object	Brand agent’s initial response
negotiated_capabilities	object	Intersection of brand and host capabilities
sponsored_context	object	Sponsored-context declaration for sponsored context in the initial response

Response Object

Field	Type	Description
message	string	Text response from brand agent
ui_elements	array	Visual components to render

Example

Request

{
  "$schema": "/schemas/sponsored-intelligence/si-initiate-session-request.json",
  "idempotency_key": "f6a7b8c9-d0e1-4234-f567-234567890123",
  "intent": "User wants to fly to Boston next Tuesday morning on flight 632 at 6 AM.",
  "media_buy_id": "delta_q1_premium_upgrade",
  "placement": "chatgpt_search",
  "offering_id": "delta_chatgpt_3313",
  "identity": {
    "consent_granted": true,
    "consent_timestamp": "2026-01-18T10:30:00Z",
    "consent_scope": ["name", "email"],
    "privacy_policy_acknowledged": {
      "brand_policy_url": "https://delta.com/privacy",
      "brand_policy_version": "2026-01"
    },
    "user": {
      "email": "[e-mail]",
      "name": "Jane Smith",
      "locale": "en-US"
    }
  },
  "supported_capabilities": {
    "modalities": {
      "conversational": true,
      "voice": true
    },
    "components": {
      "standard": ["text", "link", "image", "product_card", "carousel", "action_button"]
    },
    "commerce": {
      "acp_checkout": true
    }
  }
}

Response

{
  "$schema": "/schemas/sponsored-intelligence/si-initiate-session-response.json",
  "status": "completed",
  "session_id": "sess_abc123",
  "session_status": "active",
  "response": {
    "message": "Hi Jane! I found DL632 departing at 6:15 AM next Tuesday. Great news—as a SkyMiles Gold member, you qualify for our free Premium Economy upgrade on this flight.",
    "ui_elements": [
      {
        "type": "product_card",
        "data": {
          "title": "DL632 to Boston - Tue Jan 27",
          "subtitle": "6:15 AM → 9:42 AM (3h 27m)",
          "price": "$199",
          "badge": "Free Premium Economy Upgrade",
          "image_url": "https://delta.com/images/premium-economy.jpg",
          "cta": { "label": "Book with Upgrade", "action": "checkout" }
        }
      }
    ]
  },
  "negotiated_capabilities": {
    "modalities": {
      "conversational": true,
      "voice": true
    },
    "components": {
      "standard": ["text", "link", "image", "product_card", "carousel", "action_button"]
    },
    "commerce": {
      "acp_checkout": true
    }
  }
}

Key Points

1. intent is the conversation handoff - The host tells the brand agent what the user needs in natural language. The brand agent responds naturally, continuing the conversation. context is a separate, optional field: an opaque object (e.g., {"trace_id": "abc-123"}) that the brand agent echoes back unchanged — used by the buyer for correlation, never parsed by the brand agent.

2. Brand looks up loyalty data - If Jane’s email is recognized, Delta retrieves her SkyMiles status automatically. Hosts don’t store loyalty numbers.

3. offering_id is brand-specific - The brand interprets this reference to apply promotions, discounts, or loyalty rewards. Hosts pass it through without needing to understand offering semantics.

4. Capability negotiation - The response includes negotiated_capabilities showing what features this session can use (intersection of brand and host capabilities).

5. Sponsored context receipt - When a session follows a sponsored preflight lookup, sponsored_context_receipt records the host’s accepted use mode and disclosure commitment. This is a boundary acceptance record, not a claim about hidden model reasoning.

6. Clear PII with explicit consent - When consent_granted is true, actual email/name are passed (not hashed). This is a direct, consented handoff.