hitlslack - Human-in-the-Loop Slack

An MCP (Model Context Protocol) server that enables AI assistants to ask questions to humans via Slack and wait for their responses. This allows AI systems to request human input when they need clarification, confirmation, or access to information only humans can provide.

Features

• 🤖 Seamless AI-Human Communication: AI assistants can ask questions and receive human responses
• 💬 Slack Integration: Uses Slack threads for organized conversations
• ⏱️ Configurable Timeouts: Set custom response timeouts for your use case
• 🔄 Real-time Updates: Uses Slack Socket Mode for instant message delivery
• 🧵 Thread Management: Maintains conversation context within threads
• 📝 Type-safe: Written in TypeScript with full type safety

Installation

npm install -g hitlslack

Or use directly with npx:

npx hitlslack

Prerequisites

Slack App Setup

1. Create a Slack App:

   • Go to api.slack.com/apps
   • Click "Create New App" > "From scratch"
   • Name your app and select your workspace

2. Enable Socket Mode:

   • Go to "Socket Mode" in the left sidebar
   • Toggle "Enable Socket Mode" to ON
   • Click "Generate" under App Level Tokens
   • Token Name: socket-mode (or any name you prefer)
   • Add Scope: connections:write
   • Click "Generate"
   • Copy and save the token (starts with xapp-1-)
   • This is your SLACK_APP_TOKEN

3. Configure OAuth & Permissions:

   • Go to "OAuth & Permissions" in the left sidebar
   • Scroll down to "Scopes" section
   • Under "Bot Token Scopes", click "Add an OAuth Scope"
   • Add these scopes:
     • chat:write - Send messages as @yourapp
     • channels:history - View messages and other content in public channels
     • channels:read - View basic information about public channels
     • users:read - View people in a workspace
   • Scroll up and click "Install to Workspace"
   • Review permissions and click "Allow"
   • Copy and save the "Bot User OAuth Token" (starts with xoxb-)
   • This is your SLACK_BOT_TOKEN

4. Enable Event Subscriptions:

   • Go to "Event Subscriptions" in the left sidebar
   • Toggle "Enable Events" to ON
   • Under "Subscribe to bot events", click "Add Bot User Event"
   • Add message.channels - Listen for messages in public channels
   • Click "Save Changes" at the bottom
   • Note: Socket Mode apps don't need a Request URL

5. Add Bot to Channel:

   • In Slack, go to the channel where you want to use the bot
   • Type /invite @YourBotName (replace with your app's name)
   • The bot must be in the channel to read messages

Configuration

Environment Variables

Create a .env file or set these environment variables:

# Required
SLACK_BOT_TOKEN=xoxb-your-bot-token
SLACK_APP_TOKEN=xapp-your-app-token
SLACK_CHANNEL_ID=C1234567890  # Channel where questions will be posted
SLACK_USER_ID=U1234567890      # User to mention and accept responses from

# Optional
RESPONSE_TIMEOUT_MS=300000     # Response timeout (default: 5 minutes)
LOG_LEVEL=info                 # Log level (default: info)

Finding IDs

Channel ID

1. In Slack, right-click on the channel name
2. Select "View channel details"
3. Scroll to the bottom
4. You'll see "Channel ID: C1234567890"
5. Copy this ID (starts with C)

User ID

1. Click on the user's profile picture or name
2. Click the three dots (...) "More actions"
3. Select "Copy member ID"
4. The ID will be copied to clipboard (starts with U)

Alternatively:

• Go to your workspace settings
• Click "Manage members"
• Click on a member
• The URL will contain their ID: ...member/U1234567890

Usage

Quick Start with Claude CLI

claude mcp add slack-human \
  -s user \
  -e SLACK_BOT_TOKEN='xoxb-your-bot-token' \
  -e SLACK_APP_TOKEN='xapp-your-app-token' \
  -e SLACK_CHANNEL_ID='C1234567890' \
  -e SLACK_USER_ID='U1234567890' \
  -- npx -y hitlslack@latest

Claude Desktop Configuration

Add to your claude_desktop_config.json:

{
  "mcpServers": {
    "slack-human": {
      "command": "npx",
              "args": ["hitlslack"],
      "env": {
        "SLACK_BOT_TOKEN": "xoxb-your-bot-token",
        "SLACK_APP_TOKEN": "xapp-your-app-token",
        "SLACK_CHANNEL_ID": "C1234567890",
        "SLACK_USER_ID": "U1234567890"
      }
    }
  }
}

Claude Code Configuration

1. Set environment variables:

   export SLACK_BOT_TOKEN="xoxb-your-bot-token"
   export SLACK_APP_TOKEN="xapp-your-app-token"
   export SLACK_CHANNEL_ID="C1234567890"
   export SLACK_USER_ID="U1234567890"

2. Configure in Claude Code settings

Available Tools

ask_human

Ask a question to a human via Slack and wait for their response.

Parameters:

• question (string, required): The question to ask the human

Example:

AI: "I need to ask a human something"
Tool: ask_human({ question: "What environment should I deploy to?" })
Slack: "@user What environment should I deploy to?"
User: "Deploy to staging first"
Response: "Deploy to staging first"

reset_thread

Reset the conversation thread to start a new topic.

Parameters: None

Example:

Tool: reset_thread()
Response: "Thread reset. Next question will start a new conversation."

Development

Setup

# Clone the repository
git clone https://github.com/mkusaka/hitlslack
cd hitlslack

# Install dependencies
pnpm install

# Build the project
pnpm run build

Testing

# Run tests
pnpm test

# Run tests with coverage
pnpm run test:coverage

# Watch mode
pnpm run test:watch

Local Development

# Run in development mode
pnpm run dev

# Build and run
pnpm run build
pnpm start

# Type checking
pnpm run typecheck

# Linting
pnpm run lint

How It Works

1. AI Asks Question: The AI assistant calls the ask_human tool with a question
2. Post to Slack: The server posts the question to the configured Slack channel, mentioning the specified user
3. Wait for Response: The server listens for a response from the mentioned user in the thread
4. Return Answer: Once received, the human's response is returned to the AI assistant
5. Timeout Handling: If no response is received within the timeout period, an error is returned

Troubleshooting

Bot not responding

• Ensure the bot is invited to the channel
• Check that Socket Mode is enabled
• Verify the app-level token has connections:write scope

Authentication errors

• Regenerate tokens if they've expired
• Ensure bot token starts with xoxb- and app token with xapp-

Missing messages

• Check Event Subscriptions are enabled
• Verify message.channels event is subscribed
• Ensure the bot has required permissions

License

MIT

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.