Slack Notifier MCP

MCP server for bidirectional Slack communication with Claude Code. Get notified when tasks complete, and respond to Claude's questions directly from Slack.

Quick Start

# Add to Claude Code (one command)
claude mcp add slack-notifier -s user \
  -e SLACK_BOT_TOKEN=xoxb-your-token \
  -e SLACK_DEFAULT_CHANNEL=YOUR-CHANNEL-ID \
  -- uvx slack-notifier-mcp@latest

Features

• Send Messages - Send messages with optional urgency levels and thread support

• Ask & Wait - Ask questions and wait for replies via Slack threads

• Bidirectional - Reply to Claude from Slack, get responses back in your terminal

• Urgency Levels - Normal, important, and critical notifications with appropriate formatting

Slack App Setup

Before using this server, you need to create a Slack app:

1. Go to api.slack.com/apps and click Create New App

2. Choose From scratch, name it (e.g., "Claude Code"), and select your workspace

3. Go to OAuth & Permissions in the sidebar

4. Under Scopes > Bot Token Scopes, add:

   • chat:write - Send messages

   • channels:history - Read public channel messages

   • groups:history - Read private channel messages

   • im:history - Read DM messages

   • users:read - Get user display names

5. Click Install to Workspace at the top

6. Copy the Bot User OAuth Token (starts with xoxb-)

To get your default channel ID:

• Open Slack, right-click the channel, and select View channel details

• At the bottom, copy the Channel ID (starts with C)

Installation

Claude Code (Recommended)

claude mcp add slack-notifier -s user \
  -e SLACK_BOT_TOKEN=xoxb-your-token \
  -e SLACK_DEFAULT_CHANNEL=YOUR-CHANNEL-ID \
  -- uvx slack-notifier-mcp@latest

VS Code

code --add-mcp '{"name":"slack-notifier","command":"uvx","args":["slack-notifier-mcp@latest"],"env":{"SLACK_BOT_TOKEN":"xoxb-your-token","SLACK_DEFAULT_CHANNEL":"YOUR-CHANNEL-ID"}}'

Other MCP Clients

Add to your Claude Desktop config:

• macOS: ~/Library/Application Support/Claude/claude_desktop_config.json

• Windows: %APPDATA%\Claude\claude_desktop_config.json

• Linux: ~/.config/Claude/claude_desktop_config.json

{
  "mcpServers": {
    "slack-notifier": {
      "command": "uvx",
      "args": ["slack-notifier-mcp@latest"],
      "env": {
        "SLACK_BOT_TOKEN": "xoxb-your-token",
        "SLACK_DEFAULT_CHANNEL": "YOUR-CHANNEL-ID"
      }
    }
  }
}

1. Go to Settings → MCP → Add new MCP Server

2. Select command type

3. Enter command: uvx slack-notifier-mcp@latest

4. Add environment variables for SLACK_BOT_TOKEN and SLACK_DEFAULT_CHANNEL

Or add to ~/.cursor/mcp.json:

{
  "mcpServers": {
    "slack-notifier": {
      "command": "uvx",
      "args": ["slack-notifier-mcp@latest"],
      "env": {
        "SLACK_BOT_TOKEN": "xoxb-your-token",
        "SLACK_DEFAULT_CHANNEL": "YOUR-CHANNEL-ID"
      }
    }
  }
}

Any MCP-compatible client can use slack-notifier:

{
  "mcpServers": {
    "slack-notifier": {
      "command": "uvx",
      "args": ["slack-notifier-mcp@latest"],
      "env": {
        "SLACK_BOT_TOKEN": "xoxb-your-token",
        "SLACK_DEFAULT_CHANNEL": "YOUR-CHANNEL-ID"
      }
    }
  }
}

Local Development

git clone https://github.com/strand-ai/slack-notifier-mcp.git
cd slack-notifier-mcp
uv sync
uv run slack-notifier-mcp

MCP Tools

send

Send a message to Slack with optional urgency and thread support.

# Simple message
send(message="Build completed successfully")

# With urgency (adds formatting and @here for critical)
send(
    message="Server is down!",
    urgency="critical"  # or "normal", "important"
)

# Reply in a thread
send(
    message="Done with the first step, moving on...",
    thread_ts="1234567890.123456"
)

# Mention user
send(
    message="Need your attention",
    mention_user=True
)

Parameters:

• message (required): Message text (supports Slack mrkdwn)

• channel (optional): Channel ID or name (uses default if not set)

• thread_ts (optional): Thread timestamp to reply in a thread

• urgency (optional): normal, important, or critical

• mention_user (optional): If true, @mentions the configured user

ask_user

Send a question and wait for the user's reply.

ask_user(
    question="Should I use PostgreSQL or SQLite for the database?",
    context="Setting up the backend for the new API",
    timeout_minutes=10
)
# Returns: {"success": True, "reply": "Use PostgreSQL", ...}

Parameters:

• question (required): The question to ask

• channel (optional): Channel ID or name

• context (optional): Additional context about what you're working on

• timeout_minutes (optional): How long to wait (default 5, max 30)

get_thread_replies

Check for new replies in a thread.

get_thread_replies(
    channel="YOUR-CHANNEL-ID",
    thread_ts="1234567890.123456",
    since_ts="1234567891.000000"  # Only newer messages
)

Environment Variables

Example Usage

Tell Claude Code:

"Notify me on Slack when the tests finish running"

"Ask me on Slack whether to proceed with the database migration"

"Send a Slack notification if any errors occur while I'm away"

Debugging

Run the MCP inspector to test tools:

npx @anthropics/mcp-inspector uvx slack-notifier-mcp@latest

Check if your token works:

curl -H "Authorization: Bearer xoxb-your-token" \
  https://slack.com/api/auth.test

Development

# Install with dev dependencies
uv sync --extra dev

# Run tests
uv run pytest

# Format code
uv run black slack_mcp
uv run ruff check slack_mcp --fix

License

MIT