simple-slack-mcp-server

A simplified MCP (Model Context Protocol) server for accessing Slack API. This server allows AI assistants to interact with essential Slack messaging and channel operations through a standardized interface.

Transport Support

This server uses stdio transport only for direct integration with MCP clients like Claude Desktop.

Features

Available tools focused on core messaging and channel operations:

• slack_list_channels - List public channels in the workspace with pagination
• slack_post_message - Post a new message to a Slack channel
• slack_reply_to_thread - Reply to a specific message thread in Slack
• slack_add_reaction - Add a reaction emoji to a message
• slack_get_channel_history - Get recent messages from a channel
• slack_get_thread_replies - Get all replies in a message thread

Quick Start

Installation

npm install simple-slack-mcp-server

Configuration

You need to set the following environment variable:

• SLACK_BOT_TOKEN: Slack Bot User OAuth Token

You can create a .env file to set this environment variable:

SLACK_BOT_TOKEN=xoxb-your-bot-token

Usage

Start the MCP server

npx simple-slack-mcp-server

You can also run the installed module with node:

node node_modules/.bin/slack-mcp-server

Client Configuration

For Claude Desktop and other MCP clients:

{
  "slack": {
    "command": "npx",
    "args": [
      "simple-slack-mcp-server"
    ],
    "env": {
      "SLACK_BOT_TOKEN": "<your-bot-token>"
    }
  }
}

See examples/README.md for detailed client examples.

Required Slack Bot Permissions

Your Slack bot needs the following OAuth scopes:

• channels:read - To list channels
• chat:write - To post messages
• chat:write.public - To post in public channels
• reactions:write - To add reactions

Implementation Pattern

This server adopts the following implementation pattern:

1. Define request/response using Zod schemas

   • Request schema: Define input parameters
   • Response schema: Define responses limited to necessary fields

2. Implementation flow:

   • Validate request with Zod schema
   • Call Slack WebAPI
   • Parse response with Zod schema to limit to necessary fields
   • Return as JSON

For example, the slack_list_channels implementation parses the request with ListChannelsRequestSchema, calls slackClient.conversations.list, and returns the response parsed with ListChannelsResponseSchema.

Development

Available Scripts

• npm run dev - Start the server in development mode with hot reloading
• npm run build - Build the project for production
• npm run start - Start the production server
• npm run lint - Run linting checks (ESLint and Prettier)
• npm run fix - Automatically fix linting issues
• npm run examples - Run the example client

Contributing

1. Fork the repository
2. Create your feature branch
3. Run tests and linting: npm run lint
4. Commit your changes
5. Push to the branch
6. Create a Pull Request