# Preview or atomically create a scheduled calendar

> Markdown version of https://docs.postlake.dev/api/post-posts-calendar . The canonical page for humans.
> PostLake is the social media API for AI agents: https://postlake.dev/llms.txt

`POST /v1/posts/calendar`

Validate 1 to 200 scheduled posts as a batch. Preview with dryRun=true, then apply with the returned snapshot and a unique idempotencyKey. Either every post and the receipt are stored or none are. A cadence may assign UTC instants from startAt and everyMinutes; omit it to give each post its own scheduledAt. Credits are charged when posts publish, not when the calendar is created. Timer arming is best-effort, with the due-post runner as a backstop.

## Request

Authenticate with a bearer API key. Agents calling over MCP authorise with OAuth instead and never handle the key.

```bash
curl -X POST https://api.postlake.dev/v1/posts/calendar \
  -H "Authorization: Bearer $POSTLAKE_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"posts":[{"text":"Launch video","accounts":["acc_123"],"scheduledAt":"2026-10-01T09:00:00Z"}],"dryRun":true}'
```

### Body

| Field | Type | Required | What it is |
| --- | --- | --- | --- |
| `posts` | array of object | Yes | Normal POST /v1/posts bodies with a future scheduledAt, unless cadence assigns the times. Drafts and partial destinations are not accepted. |
| `cadence` | object | No |  |
| `cadence.startAt` | string | Yes | Timezone-qualified start instant. |
| `cadence.everyMinutes` | integer | Yes | Elapsed minutes between consecutive posts. |
| `dryRun` | boolean | Yes |  |
| `snapshot` | string | No | Required for apply; return value from preview. |
| `idempotencyKey` | string | No | Required for apply; 8 to 128 letters, digits, underscores or hyphens. |


## Response

Preview with exact UTC slots and snapshot. (`200`).

| Field | Type | Required | What it is |
| --- | --- | --- | --- |
| `dryRun` | boolean | No |  |
| `snapshot` | string | No |  |
| `matched` | integer | No |  |
| `results` | array of object | No |  |



### Example

```json
{
  "dryRun": false,
  "snapshot": "…",
  "matched": 0,
  "results": [
    {}
  ]
}
```


## Calling this from an agent

Agents do not call REST. They call tools. Over the hosted MCP server this operation is `create_scheduled_calendar`, and the agent authorises with OAuth so your API key is never pasted into a chat or seen by the model. You control what any one agent may do: which brands it may act for, which networks it may reach, how much a day, and whether it may spend credits bought up front.

## Errors

Every failure uses one shape: a stable `type`, a granular `code`, the field at fault in `param`, and a plain-language `fix`. See https://docs.postlake.dev/errors.md .

Check the result before retrying a write. Only operations that explicitly support idempotency can safely replay an `Idempotency-Key`.

## Common questions

**Can an AI agent do this without the REST API?**

Yes. Over MCP the same job is the create_scheduled_calendar tool. The agent authorises with OAuth, so no API key is pasted into a chat or seen by the model, and the answer comes back in the same normalised shape.

**Is it safe to retry this call?**

Do not automatically repeat a write after a timeout unless that endpoint explicitly documents idempotency. First read the resulting state; a second request could repeat the action.

**What happens when it fails?**

You get one error shape: a stable type, a granular code you can branch on, the offending field in param, and a fix written so an agent can correct itself rather than stop. Full list on Errors and retries.

## Related

- [Cancel a scheduled post, discard a draft, or retract a live one](https://docs.postlake.dev/api/delete-posts-by-id.md) `DELETE /v1/posts/{id}`
- [Recover a creation receipt without replaying a write](https://docs.postlake.dev/api/get-idempotency-receipt.md) `GET /v1/idempotency/{key}`
- [List posts](https://docs.postlake.dev/api/get-posts.md) `GET /v1/posts`
- [Get post](https://docs.postlake.dev/api/get-posts-by-id.md) `GET /v1/posts/{id}`