# subscribe

URL: /business/nouns/contact/subscribe · Id: `verb:Contact.subscribe` · Call: `await $.Contact.subscribe({ … })` (SDK) or the `do` tool at `https://api.sb/mcp`. Inputs says what to pass, Outputs what returns, When it waits who approves.

> Subscribe records a Contact’s chosen topics and frequency from the hosted preference page, with Consent for each topic.

Subscribe records a [Contact](/business/nouns/contact)’s chosen topics and frequency from the hosted preference page, with [Consent](/business/nouns/consent) for each topic.

## Inputs
| Input | Type | Required | Description |
| --- | --- | --- | --- |
| `contact` | [Contact](/business/nouns/contact) | Yes | The Contact. |
| `topics` | `string[]` | Yes | The topics the Contact chose. |

## Outputs
| Output | Type | Required | Description |
| --- | --- | --- | --- |
| `contact` | [Contact](/business/nouns/contact) | Yes | The Contact, with their topics. |

## Effects
- Emits [`Contact.subscribed`](/business/events/Contact.subscribed).
- Performed by the [Marketing Lead](/agents/marketing/marketing-lead).
- Two-way: it runs at once, in the `try`, `send` and `do` modes.
- Writes one Consent per topic, with its notice and time.

## Refuses when
| Check | Error | Fix | Then call |
| --- | --- | --- | --- |
| The key is valid, but its scopes do not allow this operation. | [`forbidden`](/code/api/errors/forbidden) | Use a key whose scopes cover the operation, or ask an owner of the namespace to grant them. | [Contact.subscribe](/business/nouns/contact/subscribe) |

## When it waits
| Gate | Default |
| --- | --- |
| Decision class | Low: two-way, nothing at stake |
| [Delay window](/systems/trust-and-governance/controls/one-way-windows) | None: it runs once review passes. |
| Limit | The call [Limit](/business/nouns/limit) of the [Permission](/business/nouns/permission) it runs under. |
| Over the Limit | It waits `pending` for an [Approval](/business/nouns/approval) from the [Founder](/agents/founding/founder). Approved, it runs; refused, it ends `refused` with [`limit-exceeded`](/code/api/errors/limit-exceeded); unanswered by its deadline, it ends `canceled`. |

## Example

**Ask**

```text
Subscribe the contact Tomas Berg.
```

**API**

```bash
curl -X POST https://api.sb/kilnbakery.com/contacts/contact_1/subscribe \
  -H "Authorization: Bearer $STARTUP_BUILDER_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"topics":["Example topics"]}'
```

```json
{
  "api": "https://api.sb/kilnbakery.com",
  "contact": {
    "$id": "https://api.sb/kilnbakery.com/contacts/contact_1",
    "$type": "Contact",
    "email": "tomas@kilnbakery.com",
    "phone": "Example phone"
  },
  "action": {
    "$id": "https://api.sb/kilnbakery.com/actions/action_1",
    "operation": "Contact.subscribe",
    "status": "done"
  },
  "links": {
    "self": "https://api.sb/kilnbakery.com/actions/action_1"
  }
}
```

**SDK**

```ts
import { $ } from 'startup-builder'

const contact = await $.Contact.subscribe({ contact: 'contact_1', topics: ['Example topics'] })
```

**CLI**

```bash
npx startup-builder do Contact.subscribe --json '{"contact":"contact_1","topics":["Example topics"]}'
```

**MCP**

```json
{
  "name": "do",
  "arguments": {
    "code": "return await $.Contact.subscribe({ contact: 'contact_1', topics: ['Example topics'] })"
  }
}
```