Slack MCP Server

Standalone Model Context Protocol server for Slack messaging with accountability and papertrail tracking. Built with Python, FastMCP, and slack_sdk.

Features

• Send Tool: slack_send - Send messages to users and channels
• Receive Tools (optional):
  • slack_get_messages - Fetch recent channel messages
  • slack_get_thread - Get thread replies
  • slack_list_channels - List available channels
  • slack_search_messages - Search message history
• Accountability: Automatic sender attribution on all messages
• User Resolution: Resolves usernames to Slack IDs via email lookup
• Multi-Recipient: Send to up to 10 recipients per call
• Slack Markdown: Full support for formatting, links, emoji

Setup

1. Configure

Copy .env.example to .env and set your bot token:

cp .env.example .env

SLACK_BOT_TOKEN=xoxb-your-bot-token-here
SLACK_EMAIL_DOMAIN=yourdomain.com
MAX_RECIPIENTS=10
ENABLE_RECEIVE=false
MCP_PORT=5000

Required bot scopes for sending: chat:write, chat:write.public, users:read, users:read.email

Additional scopes for receiving: channels:history, channels:read, search:read

2. Run

Docker Compose (recommended)

docker compose up -d

Docker

docker build -t slack-mcp .
docker run -p 5000:5000 --env-file .env slack-mcp

Standalone

pip install -r requirements.txt
python server.py

The server exposes an SSE endpoint at http://localhost:5000/sse.

Tools

slack_send

Send a Slack message with accountability tracking.

Parameters:

• recipients (array): Usernames, email addresses, Slack user IDs, or #channel names (max 10)
• message (string): Message content (supports Slack markdown)
• sender (string): Attribution string appended as "— Sent by {sender}"

Example:

{
  "recipients": ["jsmith", "#alerts"],
  "message": "Build completed! :tada:",
  "sender": "CI Bot"
}

Returns:

{
  "success": true,
  "sent": 2,
  "failed": 0,
  "errors": []
}

slack_get_messages (requires ENABLE_RECEIVE=true)

Fetch recent messages from a channel.

• channel (string): Channel name or ID
• limit (number): Messages to retrieve (default: 10, max: 100)

slack_get_thread (requires ENABLE_RECEIVE=true)

Get all replies in a thread.

• channel (string): Channel name or ID
• thread_ts (string): Thread timestamp from parent message

slack_list_channels (requires ENABLE_RECEIVE=true)

List all available channels with ID, name, privacy, and member count.

slack_search_messages (requires ENABLE_RECEIVE=true)

Search messages across channels. Supports Slack search operators:

• from:username, in:#channel, has:link, after:YYYY-MM-DD

Parameters:

• query (string): Search query
• count (number): Results to return (default: 20, max: 100)

Slack Markdown

• *bold*, _italic_, ~strikethrough~
• `code`, ```code block```
• <https://example.com|Link Text>
• :tada: :rocket: :white_check_mark:

Environment Variables

Variable	Required	Default	Description
SLACK_BOT_TOKEN	Yes	—	Slack Bot OAuth token
SLACK_EMAIL_DOMAIN	No	blizzard.com	Domain for username-to-email resolution
MAX_RECIPIENTS	No	10	Max recipients per message
ENABLE_RECEIVE	No	false	Enable read tools
MCP_PORT	No	5000	SSE server port

Integration

Connect to the SSE endpoint from any MCP client:

http://localhost:5000/sse