# Upload or prepare several media items

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

`POST /v1/media/batch`

Carousel helper. JSON `{ items: [{ contentType, sizeBytes }] }` returns signed five-minute PUT targets (same as MCP local upload). Multipart with multiple file parts uploads the bytes and returns MediaAsset records. Max 12 items.

## 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/media/batch \
  -H "Authorization: Bearer $POSTLAKE_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"items":["…"]}'
```

### Body

| Field | Type | Required | What it is |
| --- | --- | --- | --- |
| `items` | array of object | Yes |  |


## Response

Created (`201`).

| Field | Type | Required | What it is |
| --- | --- | --- | --- |
| `items` | array | No |  |



### Example

```json
{
  "items": [
    "…"
  ]
}
```


## Calling this from an agent

Agents do not call REST. They call tools. Over the hosted MCP server this operation is `upload_media`, 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 .

Retries are safe: send the same `Idempotency-Key` and a call that already succeeded returns its original result rather than repeating it.

## Common questions

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

Yes. Over MCP the same job is the upload_media 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?**

Yes. Send the same Idempotency-Key and a call that already succeeded returns its original result instead of repeating the work. That is what makes it safe to hand to an agent that retries on its own.

**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

- [Upload media](https://docs.postlake.dev/api/post-media.md) `POST /v1/media`
- [Complete an MCP local-file upload](https://docs.postlake.dev/api/put-media-upload.md) `PUT /media/upload`