Slack Notifier MCP Server

An MCP server that connects to Slack via Socket Mode (WebSocket) and surfaces real-time message notifications through MCP tools. No public URL or ngrok needed.

How It Works

This server runs two things simultaneously in a single process:

1. Slack Socket Mode client — connects outbound to Slack over WebSocket and receives events in real time
2. MCP server (stdio) — exposes tools to query, filter, and manage those notifications

When someone posts a message in Slack, the Socket Mode connection pushes the event to your server. The server stores it in memory (with optional disk persistence), and you can query it via the MCP tools.

Setup

1. Create a Slack App

1. Go to api.slack.com/apps and click Create New App → From scratch
2. Name it something like "Message Notifier" and pick your workspace

2. Enable Socket Mode

1. Go to Settings → Socket Mode and toggle it On
2. You'll be prompted to create an App-Level Token — name it something like "socket-mode-token"
3. Give it the connections:write scope
4. Copy the token (starts with xapp-) — this is your SLACK_APP_TOKEN

3. Subscribe to Events

1. Go to Features → Event Subscriptions and toggle it On
2. Under Subscribe to bot events, add:
   • message.channels — messages in public channels
   • message.groups — messages in private channels
   • message.im — direct messages
   • message.mpim — group direct messages
3. Save changes

4. Add Bot Token Scopes

1. Go to Features → OAuth & Permissions
2. Under Bot Token Scopes, add:
   • channels:history — read messages in public channels
   • groups:history — read messages in private channels
   • im:history — read direct messages
   • mpim:history — read group DMs
3. Install (or reinstall) the app to your workspace

5. Invite the Bot

Invite your bot to the channels you want to monitor:

/invite @Message Notifier

6. Configure the MCP Server

Add this to your Claude Desktop / Claude Code MCP config:

{
  "mcpServers": {
    "slack-notifier": {
      "command": "node",
      "args": ["/path/to/slack-notifier-mcp-server/dist/index.js"],
      "env": {
        "SLACK_APP_TOKEN": "xapp-1-your-token-here",
        "PERSIST_PATH": "/path/to/notifications.json"
      }
    }
  }
}

Environment Variables

Variable	Required	Default	Description
SLACK_APP_TOKEN	Yes	—	App-level token (xapp-...) with connections:write scope
PERSIST_PATH	No	—	File path to persist notifications across restarts

Available MCP Tools

slack_get_notifications

Retrieve stored message notifications with filtering:

• Filter by channel, read status, time range
• Pagination support
• Returns newest messages first

slack_mark_notifications_read

Mark notifications as read:

• By specific IDs
• All at once (optionally per-channel)

slack_notification_stats

Get a summary of notification counts grouped by channel — total and unread per channel.

slack_clear_notifications

Permanently delete all stored notifications (requires confirmation).

Building

npm install
npm run build

Running

SLACK_APP_TOKEN=xapp-1-... npm start

The server will connect to Slack via Socket Mode and start the MCP stdio server simultaneously.