Slack Notify MCP

Slack Webhook MCP Server

A Model Context Protocol (MCP) server for posting messages to Slack via webhooks or bot tokens.

Features

Two modes of operation: Webhooks or Bot API
Post messages to Slack channels
Support for channel overrides
Configurable bot username and emoji
Slack-specific mention support (<!channel>, <!here>, <@USERID>)
Comprehensive error handling and validation

Installation

bun install

Setup

Option 1: Webhook Mode (Simple)

Create a Slack App and Webhook:
- Go to Slack API Apps
- Create a new app or select an existing one
- Navigate to "Incoming Webhooks"
- Enable incoming webhooks
- Add a new webhook to your workspace
- Copy the webhook URL (format: https://hooks.slack.com/services/T.../B.../...)
Configure MCP Client:

{
  "mcpServers": {
    "slack-webhook": {
      "command": "bun",
      "args": [
        "run", 
        "src/index.ts",
        "--webhook-url",
        "https://hooks.slack.com/services/YOUR/SLACK/WEBHOOK",
        "--channel",
        "#general"
      ],
      "cwd": "/path/to/slack-webhook-mcp-server"
    }
  }
}

Option 2: Bot Token Mode (Advanced)

Create a Slack App with Bot Token:
- Go to Slack API Apps
- Create a new app or select an existing one
- Go to "OAuth & Permissions"
- Add bot token scopes: chat:write, chat:write.public
- Install app to workspace
- Copy the "Bot User OAuth Token" (starts with xoxb-)
Get Channel IDs:
- Right-click on channel in Slack → "View channel details" → Copy channel ID
- Or use Slack API to list channels
Configure MCP Client:

{
  "mcpServers": {
    "slack-bot": {
      "command": "bun",
      "args": [
        "run", 
        "src/index.ts",
        "--bot-token",
        "xoxb-YOUR-BOT-TOKEN",
        "--channel",
                  "CXXXXXXXXXX",
        "--username",
        "MCP Bot"
      ],
      "cwd": "/path/to/slack-webhook-mcp-server"
    }
  }
}

Usage

Command Line Arguments

Webhook Mode:

--webhook-url <url> - Slack webhook URL (required)
--channel <channel> - Default channel name (optional, e.g., "#general")

Bot Mode:

--bot-token <token> - Slack bot token (required, starts with xoxb-)
--channel <channel> - Default channel ID (required, e.g., "CXXXXXXXXXX")

Common Options:

--username <username> - Default bot username (optional)
--icon-emoji <emoji> - Default bot emoji (optional, e.g., ":")
--help - Show help message

Examples

Webhook Mode:

bun run src/index.ts \
  --webhook-url "https://hooks.slack.com/services/T00000000/B00000000/XXXXXXXXXXXXXXXXXXXXXXXX" \
  --channel "#general" \
  --username "Assistant"

Bot Mode:

bun run src/index.ts \
  --bot-token "xoxb-YOUR-BOT-TOKEN" \
  --channel "CXXXXXXXXXX" \
  --username "Assistant"

Available Tools

`post_slack_message`

Post a message to your configured Slack integration.

Parameters:

message (required): The message content to send (max 4000 characters)
channel (optional): Channel to post to (overrides default)
- Webhook mode: Channel name (e.g., "#random")
- Bot mode: Channel ID (e.g., "CXXXXXXXXXX")
username (optional): Override the default username for this message
icon_emoji (optional): Override the default emoji for this message

Example usage in MCP client:

Please post "Hello from MCP!" to the general channel

Mode Comparison

Feature	Webhook Mode	Bot Mode
Setup	Simple	Requires OAuth setup
Channel Reference	Names (#general)	IDs (CXXXXXXXXXX)
Permissions	Limited to webhook channel	Configurable scopes
Rate Limits	Higher	Standard API limits
Features	Basic messaging	Full API access
Authentication	URL-based	Token-based

Slack-Specific Features

Mentions

User mention: <@U1234567890>
Channel notification: <!channel>
Here notification: <!here>

Channel References

Webhook mode: Use #channel-name format
Bot mode: Use channel IDs like CXXXXXXXXXX

Development

Scripts

bun run start - Start the server
bun run dev - Start with file watching
bun run build - Build for production

Project Structure

slack-webhook-mcp-server/
├── package.json          # Dependencies and scripts
├── src/
│   └── index.ts         # Main server implementation  
├── types/
│   └── slack.ts         # TypeScript types and schemas
└── README.md            # This file

Error Handling

The server includes comprehensive error handling for:

Invalid webhook URLs and bot tokens
Network connectivity issues
Slack API errors (different handling for webhook vs bot)
Message length validation (4000 char limit)
Channel ID validation (bot mode)
Malformed requests

License

MIT

This server cannot be installed

security - not tested

license - permissive license

quality - not tested

How are these scores calculated?

MCP server for posting messages to Slack channels via webhooks or bot API. Supports configurable usernames, emojis, and both webhook and bot token authentication modes.

Related MCP Servers

MCP Webhook Server
kevinwatt
A
security
A
license
A
quality
Enables sending messages to webhook endpoints through the MCP protocol, supporting custom content, display names, and avatar URLs.
Last updated -
1
31
13
JavaScript
MIT License
MCP Server Discord Webhook
genm
A
security
A
license
A
quality
An MCP server that enables posting messages to Discord webhooks, allowing customization of content, username, and avatar URL.
Last updated -
1
0
JavaScript
MIT License
Slack Search MCP Server
takuya0206
-
security
F
license
-
quality
An MCP server that enables LLMs to access Slack's search functionality to retrieve users, channels, messages, and thread replies from a Slack workspace.
Last updated -
TypeScript
Slack MCP
korotovsky
A
security
A
license
A
quality
The most powerful MCP server for Slack Workspaces. This integration supports both Stdio and SSE transports, proxy settings and does not require any permissions or bots being created or approved by Workspace admins 😏.
Last updated -
2
122
Go
MIT License

View all related MCP servers