Slack Notifier

A communication skill that posts messages to Slack using incoming webhook URLs. Accepts plain text or structured Block Kit JSON for rich formatting.

94Trust High

by hermeshub-corecommunicationbeginnerv1.2.1updated Jan 15, 2026

52.3kTotal Runs

97.5%Success Rate

8.9kInstalls

94Trust Score

Required Tools

web_fetch

Inputs

Name	Type	Description	Req
webhook_url	url	Slack incoming webhook URL.	yes
message	text	Plain text message to send. Ignored if blocks are provided.	--
blocks	json	Slack Block Kit JSON array for rich formatting. Overrides message if provided.	--
channel_override	text	Override the default channel configured in the webhook.	--

Outputs

Name	Type	Description	Req
sent	boolean	Whether the message was successfully sent.	yes

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SKILL.md

---
name: slack
description: Use when you need to control Slack from the agent via the slack tool, including reacting to messages or pinning/unpinning items in Slack channels or DMs.
---

# Slack Actions

## Overview

Use slack to react, manage pins, send/edit/delete messages, and fetch member info.

## Inputs to Collect

- channelId and messageId (Slack message timestamp, e.g. 1712023032.1234)
- For reactions, an emoji (Unicode or :name:)
- For message sends, a to target (channel:<id> or user:<id>) and content

## Actions

### React to a Message

```json
{
  "action": "react",
  "channelId": "C123",
  "messageId": "1712023032.1234",
  "emoji": "✅"
}
```

### Send a Message

```json
{
  "action": "sendMessage",
  "to": "channel:C123",
  "content": "Hello from the agent"
}
```

### Edit a Message

```json
{
  "action": "editMessage",
  "channelId": "C123",
  "messageId": "1712023032.1234",
  "content": "Updated text"
}
```

### Pin a Message

```json
{
  "action": "pinMessage",
  "channelId": "C123",
  "messageId": "1712023032.1234"
}
```

### Read Recent Messages

```json
{
  "action": "readMessages",
  "channelId": "C123",
  "limit": 20
}
```

## Webhook Alternative

```bash
curl -X POST -H 'Content-type: application/json'   --data '{"text":"Hello from webhook"}'   https://hooks.slack.com/services/YOUR/WEBHOOK/URL
```

## Block Kit Example

```json
{
  "blocks": [
    {
      "type": "section",
      "text": {
        "type": "mrkdwn",
        "text": "*Alert:* System status update"
      }
    }
  ]
}
```