# trial

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

> Trial starts a Customer on an Offer free for a set number of days, with or without a card, converting or ending by its terms.

Trial starts a [Customer](/business/nouns/customer) on an [Offer](/business/nouns/offer) free for a set number of days, with or without a card, converting or ending by its terms.

## Inputs
| Input | Type | Required | Description |
| --- | --- | --- | --- |
| `offer` | [Offer](/business/nouns/offer) | Yes | The Offer to try. |
| `customer` | [Customer](/business/nouns/customer) | Yes | The Customer who tries it. |
| `days` | `integer` | Yes | How long the trial runs. Never randomized. |
| `card` | `boolean` | No | True to take a card up front and charge it when the trial ends. |

## Outputs
| Output | Type | Required | Description |
| --- | --- | --- | --- |
| `subscription` | [Subscription](/business/nouns/subscription) | Yes | The Subscription, free until the trial ends. |
| `offer` | [Offer](/business/nouns/offer) | Yes | The Offer the trial is on. |

## Effects
- Emits [`Offer.trialed`](/business/events/Offer.trialed).
- Performed by the [Billing Specialist](/agents/finance/billing-specialist).
- Two-way: it runs at once, in the `try`, `send` and `do` modes.
- With a card on file, converts to a paid Subscription at the end unless canceled first.
- Without a card, ends at the end and opens a conversion Task for the Success Manager.

## 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. | [Offer.trial](/business/nouns/offer/trial) |

## 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
Trial the offer “Résumé review” with a customer.
```

**API**

```bash
curl -X POST https://api.sb/quietcopy.com/offers/offer_1/trial \
  -H "Authorization: Bearer $STARTUP_BUILDER_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"customer":"customer_1","days":1}'
```

```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.trial",
    "status": "done"
  },
  "links": {
    "self": "https://api.sb/quietcopy.com/actions/action_1"
  }
}
```

**SDK**

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

const { subscription, offer } = await $.Offer.trial({ offer: 'offer_1', customer: 'customer_1', days: 1 })
```

**CLI**

```bash
npx startup-builder do Offer.trial --json '{"offer":"offer_1","customer":"customer_1","days":1}'
```

**MCP**

```json
{
  "name": "do",
  "arguments": {
    "code": "return await $.Offer.trial({ offer: 'offer_1', customer: 'customer_1', days: 1 })"
  }
}
```

Guides that call it: [Give a customer a free trial](/products/offers/give-a-free-trial).