# Play programs: apply

URL: /code/mcp/play/verbs · Id: `page:code/mcp/play/verbs`

> The Play Verbs apply as MCP do programs, with inputs, result, refusals and an example.

Reference for [Play](/business/nouns/play), one group of [Play programs](/code/mcp/play).

### Play.apply
Apply runs a Play across a Portfolio cohort, one wave at a time, measured as an Experiment. [Verb page](/business/nouns/play/apply?interface=mcp).

```text
do: return await $.Play.apply(input)
```

Emits [`Play.applied`](/business/events/Play.applied).

**Inputs**

| Input | Type | Required | Description |
| --- | --- | --- | --- |
| `play` | [Play](/business/nouns/play) | Yes | The Play to run. |
| `cohort` | `string` | Yes | The Portfolio query that selects the Startups. |

**Returns**

| Output | Type | Required | Description |
| --- | --- | --- | --- |
| `experiment` | [Experiment](/business/nouns/experiment) | Yes | The Experiment that measures the rollout. |
| `play` | [Play](/business/nouns/play) | Yes | The Play applied. |

**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. | None. |
| 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. | None. |

**Example**

```json
{
  "name": "do",
  "arguments": {
    "code": "return await $.Play.apply({ play: 'play_hr4WTcrAyZ', cohort: 'Example cohort' })"
  }
}
```