AdCP — si_initiate

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
`context`	string	Yes	Natural language description of user intent
`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

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/3.0.0-rc.2/sponsored-intelligence/si-initiate-session-request.json",
  "context": "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": "jane@example.com",
      "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/3.0.0-rc.2/sponsored-intelligence/si-initiate-session-response.json",
  "session_id": "sess_abc123",
  "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

Context is a conversation handoff - The host tells the brand agent what the user needs. The brand agent responds naturally, continuing the conversation.
Brand looks up loyalty data - If Jane’s email is recognized, Delta retrieves her SkyMiles status automatically. Hosts don’t store loyalty numbers.
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.
Capability negotiation - The response includes negotiated_capabilities showing what features this session can use (intersection of brand and host capabilities).
Clear PII with explicit consent - When consent_granted is true, actual email/name are passed (not hashed). This is a direct, consented handoff.

Getting Started

Building with AdCP

Protocol

FAQ

Trust & Security

Reference

Certification

si_initiate_session

Request

Offering Token

Identity Object

Supported Capabilities Object

Response

Response Object

Example

Request

Response

Key Points

​Request

​Offering Token

​Identity Object

​Supported Capabilities Object

​Response

​Response Object

​Example

​Request

​Response

​Key Points

Request

Offering Token

Identity Object

Supported Capabilities Object

Response

Response Object

Example

Request

Response

Key Points