> For the complete documentation index, see [llms.txt](https://agpt.co/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://agpt.co/docs/integrations/block-integrations/blocks.md).

# Slack Blocks

Blocks for sending messages to Slack channels, direct messages, and threads using a Slack Bot Token.

## Send Slack Message

### What it is

Send a text message to any Slack channel, DM, or thread. Required bot token scope: chat:write.

### How it works

Calls the Slack `chat.postMessage` API with your bot token. The token must have the `chat:write` scope. Optionally uses `chat:write.customize` to set a custom username or icon emoji. Returns the message timestamp (`ts`), which can be passed back as `thread_ts` to reply in the same thread.

If the Slack API returns a non-`ok` response (e.g. `invalid_auth`, `channel_not_found`, `not_in_channel`, or missing scopes), the block raises a user-facing error with the Slack error code so you can diagnose and fix the issue. Network failures and unexpected exceptions are also surfaced as errors through the block's `error` output.

### Inputs

| Input         | Description                                                                                                         | Type | Required |
| ------------- | ------------------------------------------------------------------------------------------------------------------- | ---- | -------- |
| channel       | Channel ID (e.g. C1234567890) or name (e.g. #general). For DMs use the user's member ID (e.g. U1234567890).         | str  | Yes      |
| text          | Message text. Supports Slack mrkdwn: *bold*, *italic*, `code`, <https://example.com\\|link>.                        | str  | Yes      |
| thread\_ts    | Timestamp of the parent message to reply in a thread. Use the 'ts' output from a previous Send Slack Message block. | str  | No       |
| username      | Custom display name for the bot in this message. Requires chat:write.customize scope.                               | str  | No       |
| icon\_emoji   | Emoji to use as the bot's icon (e.g. :robot:). Requires chat:write.customize scope.                                 | str  | No       |
| unfurl\_links | Automatically expand URLs into rich previews.                                                                       | bool | No       |
| mrkdwn        | Enable Slack markdown formatting in the message text.                                                               | bool | No       |

### Outputs

| Output  | Description                                                                              | Type |
| ------- | ---------------------------------------------------------------------------------------- | ---- |
| error   | Error message if the operation failed                                                    | str  |
| ts      | Message timestamp — Slack's unique message ID. Use as 'thread\_ts' to reply in a thread. | str  |
| channel | The channel ID where the message was posted.                                             | str  |

### Possible use case

**Daily Summaries**: Post a recap of completed tasks or pipeline results to a `#updates` channel at the end of each run.

**Anomaly Alerts**: Send an immediate notification to a `#alerts` channel when a monitoring workflow detects an error or threshold breach.

**Threaded Follow-ups**: Chain two Send Slack Message blocks — pass the `ts` output of the first into the `thread_ts` input of the second to keep responses organized in a single thread.

***


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