URL: /code/apps/analytics-and-experiments/watch · Id: `page:/code/apps/analytics-and-experiments/watch`

# Metric.watch

> Opens a Task, or sends you a Message, the day a number crosses the line you set.

POST https://api.sb/{your-domain}/metrics/{metric}/watch

Opens a [Task](https://startupbuilder.dev/business/nouns/task), or sends you a [Message](https://startupbuilder.dev/business/nouns/message), the day a number crosses the line you set.

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

```text title="Run it · Ask"
Tell me if the reply rate drops under 3%.
```

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

const result = await $.try.Metric.watch({ metric: 'https://api.sb/leaseline.app/metrics/metric_reply-rate', threshold: 0.03, direction: 'below' })
```

```json title="Run it · Response"
{
  "api": "https://api.sb/leaseline.app",
  "metric": {
    "$id": "https://api.sb/leaseline.app/metrics/metric_reply-rate",
    "$type": "Metric"
  },
  "watch": {
    "$id": "https://api.sb/leaseline.app/watches/watch_Rr2bW8tQ5n",
    "$type": "Watch"
  },
  "action": {
    "operation": "Metric.watch",
    "mode": "try",
    "status": "done"
  }
}
```

Its Inputs, Outputs, Effects and guards quote [the hub’s `Metric.watch`](https://startupbuilder.dev/business/nouns/metric/watch); 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 [Analytics and experiments](/code/apps/analytics-and-experiments#verbs).

## Inputs
| Name | Type | Default | Meaning |
| --- | --- | --- | --- |
| `metric` | `Metric` | Required | The Metric to watch. |
| `threshold` | `number` | Required | The value that trips it. |
| `direction` | `string` | Required | Trip when the Metric goes above or below the threshold. |

## Outputs
| Field | Type | What `null` means |
| --- | --- | --- |
| `watch` | `Watch` | Never null: the Watch that checks it. |
| `metric` | `Metric` | Never null: the Metric now watched. |

## 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; `Metric.watched` 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**

A guardrail Metric that trips stops its Experiment at once, with no delay window.

**Emits**

`Metric.watched` with `{ metric }`

**Performed by**

[Analyst](https://startupbuilder.dev/agents/marketing/analyst)

**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 `Metric.watched` delivers the result.

**Ask**

```text
Tell me if the reply rate drops under 3%.
```

**API**

```bash
curl -X POST "https://api.sb/leaseline.app/metrics/metric_reply-rate/watch?mode=send" \
  -H "Authorization: Bearer $SB_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
  "threshold": 0.03,
  "direction": "below"
}'
```

**CLI**

```bash
npx startup-builder do Metric.watch --send --data '{
  "threshold": 0.03,
  "direction": "below"
}'
```

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

**MCP**

```json
{
  "name": "do",
  "arguments": {
    "mode": "send",
    "code": "return await $.Metric.watch({ threshold: 0.03, direction: 'below' })"
  }
}
```

**SDK**

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

const result = await $.send.Metric.watch({
  metric: 'https://api.sb/leaseline.app/metrics/metric_reply-rate',
  threshold: 0.03,
  direction: 'below',
})
```


```json title="Response, in send mode"
{
  "mode": "send",
  "action": {
    "$id": "https://api.sb/leaseline.app/actions/action_Sd3kQ9vT2w",
    "operation": "Metric.watch",
    "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
- **Workflows:** [Weekly readout](/capabilities/measure/weekly-readout)
- **Jobs:** [Convert visitors](/capabilities/convert-visitors) · [Keep and grow customers](/capabilities/keep-and-grow) · [Measure](/capabilities/measure)

## Related
[`Metric.query`](/code/apps/analytics-and-experiments/query) · [`Experiment.start`](/code/apps/analytics-and-experiments/start) · [`Experiment.conclude`](/code/apps/analytics-and-experiments/conclude) · [`Dashboard.ask`](/code/apps/analytics-and-experiments/ask) · [`Metric.define`](/code/apps/analytics-and-experiments/define) · [`Event.capture`](/code/apps/analytics-and-experiments/capture) · [`Hypothesis.test`](/code/apps/analytics-and-experiments/test) · [`Dashboard.schedule`](/code/apps/analytics-and-experiments/schedule)