# Save a post

> Save an X post to the user's library by its id. Use library.save_by_url for a URL.

`library.save` · write

- **MCP tool:** `library_save`. Catalog: reach it with `find_actions` and `run_write_action`, or turn on the full toolset.
- **REST:** `POST /v1/library/save`
- **CLI:** `xholic library save`
- **Scope:** `write`
- **Plan:** Every plan, including the trial
- **Cost:** Free.
- **Rate limit bucket:** `write`
- **Undo:** from the activity log, which runs `library.unsave` (not offered when `alreadySaved` is true: the call changed nothing)

## Input

| Field | Type | Required | Description |
| --- | --- | --- | --- |
| `tweetId` | string | Yes | X post id (digits). |
| `account` | string ≤ 64 chars | No | X account to act on, as @handle. Leave it out to use the connection's default account. |
| `dryRun` | boolean | No | Return exactly what would happen without doing it. |
| `idempotencyKey` | string ≤ 200 chars | No | A unique key for this write. Repeating a call with the same key returns the first result instead of acting twice. |