> ## Documentation Index
> Fetch the complete documentation index at: https://docs.adcontextprotocol.org/llms.txt
> Use this file to discover all available pages before exploring further.

# 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.

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`](./si_get_offering) lookup before initiating, include the token for **session continuity**:

```json theme={null}
{
  "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:

```json theme={null}
{
  "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

```json theme={null}
{
  "$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

```json theme={null}
{
  "$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

1. **Context is a conversation handoff** - The host tells the brand agent what the user needs. The brand agent responds naturally, continuing the conversation.

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.