Slack API MCP Server

Comprehensive Slack operations MCP server built with xmcp. Provides 12 tools for Slack messaging, channel management, user info, and file uploads.

Tools

• post_message - Post messages to channels/threads (Block Kit only)
• update_message - Edit existing messages (Block Kit only)
• delete_message - Delete messages
• add_reaction - Add emoji reactions
• pin_message - Pin messages to channels
• get_channel_context - Fetch message history with user name resolution
• get_user_info - Get user information
• list_channels - List accessible channels
• upload_snippet - Upload text files/snippets (code, logs, etc.)
• get_image_from_slack - Download images from Slack
• create_channel - Create new Slack channels
• invite_users - Invite users to channels

Features

• Block Kit enforcement: post_message and update_message only accept Block Kit blocks
• Compact formatting: Optional 60-90% size reduction for API responses
• Smart caching: 5min TTL cache for users/channels with LRU eviction

Environment Variables

# Required
SLACK_BOT_TOKEN=xoxb-your-bot-token

Copy .env.example to .env and fill in your credentials.

Installation

# Clone repository
git clone https://github.com/yourusername/slack-api-mcp.git
cd slack-api-mcp

# Install dependencies
pnpm install

# Build server
pnpm build

Development

# Install dependencies
pnpm install

# Build server
pnpm build

# Start server (STDIO transport)
pnpm start:stdio

Usage

Add to .mcp.json:

{
  "mcpServers": {
    "slack-api": {
      "command": "node",
      "args": ["/absolute/path/to/slack-api-mcp/dist/stdio.js"],
      "env": {
        "SLACK_BOT_TOKEN": "${SLACK_BOT_TOKEN}"
      }
    }
  }
}

Or use .mcp.json in your project root:

{
  "mcpServers": {
    "slack-api": {
      "command": "node",
      "args": ["./dist/stdio.js"],
      "env": {
        "SLACK_BOT_TOKEN": "${SLACK_BOT_TOKEN}"
      }
    }
  }
}

Architecture

Built with xmcp framework:

• Tools auto-discovered from src/tools/ directory
• Shared utilities in src/lib/: caching, formatting, Slack client singleton
• STDIO transport for Claude Code integration

License

MIT