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
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

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

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