URL: /code/apps/forms-and-waitlists/join · Id: `page:/code/apps/forms-and-waitlists/join`

# Waitlist.join

> Adds a lead to the Waitlist for an offer that is not open to them yet.

POST https://api.sb/{your-domain}/waitlists/{waitlist}/join

Adds a [lead](https://startupbuilder.dev/business/nouns/lead) to the [Waitlist](https://startupbuilder.dev/business/nouns/waitlist) for an [offer](https://startupbuilder.dev/business/nouns/offer) that is not open to them yet.

- **Action class:** None
- **Approval:** Runs on its own
- **Emits:** `Waitlist.joined`
- **Price:** Free

```text title="Run it · Ask"
Add rosa@northgate-rentals.com to the owner-statements waitlist.
```

```ts title="Run it · SDK"
import { $ } from 'startup-builder'

const result = await $.try.Waitlist.join({ waitlist: 'https://api.sb/leaseline.app/waitlists/waitlist_Gm7hJ3kL6a', email: 'rosa@northgate-rentals.com' })
```

```json title="Run it · Response"
{
  "api": "https://api.sb/leaseline.app",
  "waitlist": {
    "$id": "https://api.sb/leaseline.app/waitlists/waitlist_Gm7hJ3kL6a",
    "$type": "Waitlist",
    "size": 38
  },
  "lead": {
    "$id": "https://api.sb/leaseline.app/leads/lead_Ro5aL2vZ1e",
    "$type": "Lead",
    "status": "new",
    "source": "waitlist"
  },
  "action": {
    "operation": "Waitlist.join",
    "mode": "try",
    "status": "done"
  }
}
```

Its Inputs, Outputs, Effects and guards quote [the hub’s `Waitlist.join`](https://startupbuilder.dev/business/nouns/waitlist/join); this page adds what each Venue honors, its limits and a worked call. It is one of the [Verbs](https://startupbuilder.dev/business/nouns/verb) of [Forms and waitlists](/code/apps/forms-and-waitlists#verbs).

## Inputs
| Name | Type | Default | Meaning |
| --- | --- | --- | --- |
| `waitlist` | `Waitlist` | Required | The Waitlist to join. |
| `email` | `email` | Required | Where to reach the lead. |

## Outputs
| Field | Type | What `null` means |
| --- | --- | --- |
| `lead` | `Lead` | Never null: the waiting lead. |
| `waitlist` | `Waitlist` | Never null: the Waitlist joined. |

## Effects
**Action class**

None: no approval rule names it, so it runs within its seat’s Permissions and Limits

**Modes**

- `try`: Runs every check and returns the record as it would be; nothing is stored.
- `send`: Returns a pending Action at once; `Waitlist.joined` fires when it is done.
- `do`: Waits for the Action to finish and returns the record.

**Idempotency**

Only with a key: the same `Idempotency-Key` and input return the first Action, and the same key with other input returns `409`.

**Saved or shared**

The Waitlist is saved as the call leaves it, with the Action that changed it.

**Emits**

`Waitlist.joined` with `{ waitlist }`

**Performed by**

Whichever seat calls it

**Price**

Free on your own account: the platform charges nothing for the call.

## On each Venue
It acts on your own records and reaches no Venue, so every account answers the same way.

## What try does
Runs every check the call meets and returns the record as it would be; nothing is stored, sent or posted.

## Refuses when
The hub sets no guard of its own on this call: it refuses only on the shared checks every write meets (a missing record, a Permission the seat lacks).

## When it waits
Returns in one response; nothing waits.

## Example
In `send` mode the call returns its pending Action at once, and `Waitlist.joined` delivers the result.

**Ask**

```text
Add rosa@northgate-rentals.com to the owner-statements waitlist.
```

**API**

```bash
curl -X POST "https://api.sb/leaseline.app/waitlists/waitlist_Gm7hJ3kL6a/join?mode=send" \
  -H "Authorization: Bearer $SB_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
  "email": "rosa@northgate-rentals.com"
}'
```

**CLI**

```bash
npx startup-builder do Waitlist.join --send --data '{
  "email": "rosa@northgate-rentals.com"
}'
```

`--send` returns the pending Action at once.

**MCP**

```json
{
  "name": "do",
  "arguments": {
    "mode": "send",
    "code": "return await $.Waitlist.join({ email: 'rosa@northgate-rentals.com' })"
  }
}
```

**SDK**

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

const result = await $.send.Waitlist.join({
  waitlist: 'https://api.sb/leaseline.app/waitlists/waitlist_Gm7hJ3kL6a',
  email: 'rosa@northgate-rentals.com',
})
```


```json title="Response, in send mode"
{
  "mode": "send",
  "action": {
    "$id": "https://api.sb/leaseline.app/actions/action_Sd3kQ9vT2w",
    "operation": "Waitlist.join",
    "status": "pending",
    "reason": "running"
  }
}
```

To retry, send the same `Idempotency-Key`: the retry returns the first answer for $0. A new key reads again.

## Used by
None.

## Related
[`Waitlist.admit`](/code/apps/forms-and-waitlists/admit) · [`Visitor.identify`](/code/apps/forms-and-waitlists/identify) · [`Visitor.merge`](/code/apps/forms-and-waitlists/merge) · [`Form.create`](/code/apps/forms-and-waitlists/create) · [`Form.update`](/code/apps/forms-and-waitlists/update)