# subscribe

URL: /business/nouns/offer/subscribe · Id: `verb:Offer.subscribe` · Call: `await $.Offer.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 accepts a recurring Offer as a Subscription that renews each period until it ends.

Subscribe accepts a recurring [Offer](/business/nouns/offer) as a [Subscription](/business/nouns/subscription) that renews each period until it ends.

## Inputs
| Input | Type | Required | Description |
| --- | --- | --- | --- |
| `offer` | [Offer](/business/nouns/offer) | Yes | The recurring Offer. |
| `quantity` | `integer` | No | Seats or units. Defaults to 1. |
| `promotionCode` | `string` | No | A promotion code the buyer typed; applies its Coupon for the Coupon’s duration. |

## Outputs
| Output | Type | Required | Description |
| --- | --- | --- | --- |
| `subscription` | [Subscription](/business/nouns/subscription) | Yes | The new Subscription. |
| `offer` | [Offer](/business/nouns/offer) | Yes | The Offer subscribed to. |

## Effects
- Emits [`Offer.subscribed`](/business/events/Offer.subscribed).
- Performed by the [Billing Specialist](/agents/finance/billing-specialist).
- Makes the party a Customer when it is not one yet.
- Grants the Entitlements the Offer includes.
- Bills the first period.

## Refuses when
| Check | Error | Fix | Then call |
| --- | --- | --- | --- |
| The input does not match the schema of the operation. | [`invalid-input`](/code/api/errors/invalid-input) | Read the schema of the operation, then send every required field with the right type. | [Offer.subscribe](/business/nouns/offer/subscribe) |
| The operation is part of an Offer the caller has not accepted or paid for. | [`payment-required`](/code/api/errors/payment-required) | Accept the Offer named in the response, then retry the call. | [Offer.accept](/business/nouns/offer/accept) |
| 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. | [Offer.subscribe](/business/nouns/offer/subscribe) |
| The record is not in a state that allows this Verb, so the call is refused. | [`refused`](/code/api/errors/refused) | Read the record, run the Verb that moves it to an allowed state, then retry. | [Offer.subscribe](/business/nouns/offer/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 a customer to the offer “Résumé review”.
```

**API**

```bash
curl -X POST https://api.sb/quietcopy.com/offers/offer_1/subscribe \
  -H "Authorization: Bearer $STARTUP_BUILDER_API_KEY"
```

```json
{
  "api": "https://api.sb/quietcopy.com",
  "subscription": {
    "$id": "https://api.sb/quietcopy.com/subscriptions/subscription_1",
    "$type": "Subscription",
    "status": "active"
  },
  "offer": {
    "$id": "https://api.sb/quietcopy.com/offers/offer_1",
    "$type": "Offer",
    "price": {
      "amount": 39,
      "currency": "USD"
    }
  },
  "action": {
    "$id": "https://api.sb/quietcopy.com/actions/action_1",
    "operation": "Offer.subscribe",
    "status": "done"
  },
  "links": {
    "self": "https://api.sb/quietcopy.com/actions/action_1"
  }
}
```

**SDK**

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

const { subscription, offer } = await $.Offer.subscribe({ offer: 'offer_1' })
```

**CLI**

```bash
npx startup-builder do Offer.subscribe --json '{"offer":"offer_1"}'
```

**MCP**

```json
{
  "name": "do",
  "arguments": {
    "code": "return await $.Offer.subscribe({ offer: 'offer_1' })"
  }
}
```

Next: [`Role.staff`](/business/nouns/role/staff) (in `guide:buy-a-specialist-agent-for-a-seat`).

Guides that call it: [Buy a specialist agent for a seat](/agents/buy-a-specialist-agent-for-a-seat).