Ask on Slack MCP Server

A Model Context Protocol (MCP) server that enables AI assistants to request information from humans via Slack. This server acts as a bridge between AI systems and human experts, allowing AI to ask questions and receive responses through Slack when it needs human knowledge or clarification.

Features

• MCP-compliant server for AI assistant integration

• Two transport modes: stdio (for MCP clients) and HTTP (for web-based clients)

• Slack integration via HTTP polling with thread-based conversations

• Smart fallback: Works with or without build step

• Multiple deployment options: Bun, npm, global installation

• Comprehensive logging with configurable levels and file output

• Secure token handling via environment variables or CLI arguments

Related MCP server: AskOnSlackMCP

Quick Start

Using Bun (Recommended)

# Run directly without installation
bunx @rodrigolive/ask-on-slack stdio \
  --slack-bot-token "xoxb-your-bot-token" \
  --slack-app-token "xapp-your-app-token" \
  --slack-channel-id "C1234567890" \
  --slack-user-id "U1234567890"

Using npm

# Run directly without installation
npx @rodrigolive/ask-on-slack stdio \
  --slack-bot-token "xoxb-your-bot-token" \
  --slack-app-token "xapp-your-app-token" \
  --slack-channel-id "C1234567890" \
  --slack-user-id "U1234567890"

Using Environment Variables

export ASK_SLACK_BOT="xoxb-your-bot-token"
export ASK_SLACK_APP="xapp-your-app-token"
export ASK_SLACK_CHANNEL="C1234567890"
export ASK_SLACK_USER="U1234567890"

# Now run without arguments
bunx @rodrigolive/ask-on-slack stdio

Transport Modes

Stdio Mode (Default for MCP Clients)

Use stdio mode for MCP clients like Claude Desktop:

bunx @rodrigolive/ask-on-slack stdio [options]

HTTP Mode (For Web Clients)

Use HTTP mode for web-based MCP clients:

bunx @rodrigolive/ask-on-slack serve [options]

The HTTP server will listen on port 3000 (or specified port) at the /mcp endpoint.

How It Works in Slack

The server supports three different Slack interaction modes:

1. Channel + User Mention: If both ASK_SLACK_CHANNEL and ASK_SLACK_USER are set, the bot posts questions in the channel mentioning the user and listens for replies in the thread.

2. Channel Only: If only ASK_SLACK_CHANNEL is set, the bot posts questions in the channel (without mention) and listens for the first reply in the thread.

3. Direct Message: If only ASK_SLACK_USER is set, the bot opens a direct message to the user.

Important: The bot must be invited to the channel if using a public or private channel.

Prerequisites

Slack App Setup

1. Create a new Slack app at https://api.slack.com/apps

2. Install the app to your workspace

3. Configure the required permissions

Required Bot Token Scopes

Your app needs these Bot Token Scopes:

• chat:write - Send messages to channels

• channels:read - Access channel information

• users:read - Access user information

App-Level Token

An App-Level Token is required for the HTTP polling functionality.

Installation Options

Global Installation

# Using Bun
bun install -g @rodrigolive/ask-on-slack

# Using npm
npm install -g @rodrigolive/ask-on-slack

Then run directly:

ask-on-slack stdio --slack-bot-token "xoxb-your-token" --slack-app-token "xapp-your-token"

Local Development

# Clone the repository
git clone https://github.com/rodrigolive/ask-on-slack-mcp.git
cd ask-on-slack-mcp

# Install dependencies
bun install

# Run in development mode (no build required)
bun run dev

# Or build and run
bun run build
bun run start

Configuration

Command-Line Arguments

• --slack-bot-token - Bot User OAuth Token (xoxb-...)

• --slack-app-token - App-Level Token (xapp-...)

• --slack-channel-id - Channel ID where the bot will operate

• --slack-user-id - User ID to mention when asking questions

• --role, -r - Role for the human (boss, expert, or custom name)

• --log-level - Logging level (default: INFO)

• --log-file - Log file path (if specified, logs will be written to file instead of stderr)

• --port - Port to listen on for HTTP mode (default: 3000)

Environment Variables

• ASK_SLACK_BOT - Bot User OAuth Token (xoxb-...)

• ASK_SLACK_APP - App-Level Token (xapp-...)

• ASK_SLACK_CHANNEL - Channel ID where the bot will operate

• ASK_SLACK_USER - User ID to mention when asking questions

• ASK_SLACK_ROLE - Role for the human (boss, expert, or custom name)

• LOG_LEVEL - Logging level (default: INFO)

• LOG_FILE - Log file path

• PORT - Port for HTTP mode (default: 3000)

Role Configuration

The server supports different roles for the human you're asking questions to. Each role changes the tool names and descriptions to match the context.

Available Roles

boss (Default)

• When to use: When you need approval, decisions, or information that requires authority

• Tool names: ask_the_boss_on_slack, clarify_with_the_boss_on_slack, acknowledge_the_boss_on_slack

• Description: Focused on preferences, project-specific context, local environment details, non-public information, and decisions

expert

• When to use: When you need to confirm expert details, validate technical information, or get expert opinion

• Tool names: ask_the_expert_on_slack, clarify_with_the_expert_on_slack, acknowledge_the_expert_on_slack

• Description: Focused on technical details, verification, specialized knowledge, and expert confirmation

Custom Role

• When to use: When you want a generic role that doesn't assume boss or expert context

• Tool names: ask_the_human_on_slack, clarify_with_the_human_on_slack, acknowledge_the_human_on_slack

• Description: Generic human interaction for any type of question or assistance

Role Examples

# Use boss role (default)
bunx @rodrigolive/ask-on-slack stdio

# Use expert role
bunx @rodrigolive/ask-on-slack stdio --role expert

# Use custom role
bunx @rodrigolive/ask-on-slack stdio --role consultant

# Using environment variable
export ASK_SLACK_ROLE="expert"
bunx @rodrigolive/ask-on-slack stdio

MCP Client Configuration

Claude Desktop Configuration

Add to your Claude Desktop configuration (~/Library/Application Support/Claude/claude_desktop_config.json):

Using Bun (Recommended)

{
  "mcpServers": {
    "ask-on-slack": {
      "command": "bunx",
      "args": [
        "@rodrigolive/ask-on-slack",
        "stdio",
        "--slack-bot-token", "xoxb-your-actual-token",
        "--slack-app-token", "xapp-your-actual-token", 
        "--slack-channel-id", "C1234567890",
        "--slack-user-id", "U1234567890"
      ]
    }
  }
}

Using npm

{
  "mcpServers": {
    "ask-on-slack": {
      "command": "npx",
      "args": [
        "@rodrigolive/ask-on-slack",
        "stdio",
        "--slack-bot-token", "xoxb-your-actual-token",
        "--slack-app-token", "xapp-your-actual-token", 
        "--slack-channel-id", "C1234567890",
        "--slack-user-id", "U1234567890"
      ]
    }
  }
}

Using Environment Variables

{
  "mcpServers": {
    "ask-on-slack": {
      "command": "bunx",
      "args": ["@rodrigolive/ask-on-slack", "stdio"],
      "env": {
        "ASK_SLACK_BOT": "xoxb-your-token",
        "ASK_SLACK_APP": "xapp-your-token",
        "ASK_SLACK_CHANNEL": "C1234567890",
        "ASK_SLACK_USER": "U1234567890"
      }
    }
  }
}

Global Installation

{
  "mcpServers": {
    "ask-on-slack": {
      "command": "ask-on-slack",
      "args": [
        "stdio",
        "--slack-bot-token", "xoxb-your-token",
        "--slack-app-token", "xapp-your-token",
        "--slack-channel-id", "C1234567890",
        "--slack-user-id", "U1234567890"
      ]
    }
  }
}

HTTP Mode Configuration

For web-based MCP clients, use HTTP mode:

{
  "mcpServers": {
    "ask-on-slack": {
      "command": "bunx",
      "args": [
        "@rodrigolive/ask-on-slack",
        "serve",
        "--port", "3000",
        "--slack-bot-token", "xoxb-your-token",
        "--slack-app-token", "xapp-your-token",
        "--slack-channel-id", "C1234567890",
        "--slack-user-id", "U1234567890"
      ]
    }
  }
}

The server will be available at http://localhost:3000/mcp.

Codex Configuration

For Codex, add to your configuration file (~/.codex/config.toml):

[mcp.servers.ask-on-slack]
command = "bunx"
args = [
  "@rodrigolive/ask-on-slack",
  "stdio",
  "--slack-bot-token", "xoxb-your-token",
  "--slack-app-token", "xapp-your-token",
  "--slack-channel-id", "C1234567890",
  "--slack-user-id", "U1234567890"
]

Or using environment variables:

[mcp.servers.ask-on-slack]
command = "bunx"
args = ["@rodrigolive/ask-on-slack", "stdio"]

[mcp.servers.ask-on-slack.env]
ASK_SLACK_BOT = "xoxb-your-token"
ASK_SLACK_APP = "xapp-your-token"
ASK_SLACK_CHANNEL = "C1234567890"
ASK_SLACK_USER = "U1234567890"

Note: Codex only supports stdio mode, so always use the stdio command.

Available Tools

The server provides three MCP tools for interacting with humans via Slack. The tool names and descriptions change based on the selected role:

Dynamic Tool Names

The tool names are dynamically generated based on the role:

• Boss role: ask_the_boss_on_slack, clarify_with_the_boss_on_slack, acknowledge_the_boss_on_slack

• Expert role: ask_the_expert_on_slack, clarify_with_the_expert_on_slack, acknowledge_the_expert_on_slack

• Custom role: ask_the_human_on_slack, clarify_with_the_human_on_slack, acknowledge_the_human_on_slack

Tool Types

1. Ask Tool (ask_the_{role}_on_slack)

Purpose: Main tool for asking questions to humans via Slack when you need information that only they would know.

When to use:

• Boss role: Use for preferences, project-specific context, local environment details, non-public information, or when you have doubts

• Expert role: Use when you need to confirm expert details, validate technical information, or get expert opinion

• Custom role: Use when you need human perspective, local information, or confirmation that only a human can provide

Parameters:

• question (string): The question to ask the human. Be specific and provide context.

Example (Boss role):

{
  "tool": "ask_the_boss_on_slack",
  "arguments": {
    "question": "What is the API endpoint for the production server?"
  }
}

Example (Expert role):

{
  "tool": "ask_the_expert_on_slack",
  "arguments": {
    "question": "Can you verify if this database schema design follows best practices?"
  }
}

Important: If the user replies with another question, call this tool again.

2. Clarify Tool (clarify_with_the_{role}_on_slack)

Purpose: Re-ask a question in a clearer way if the human didn't understand your original question or asked something back.

When to use: If you called the ask tool but the human did not understand your question or asked anything back, you MUST use this tool to re-ask in a clearer way. Do not use this tool if you have not called the ask tool before.

Parameters:

• question (string): The clarification to ask the human. Be specific and provide context.

Example:

{
  "tool": "clarify_with_the_boss_on_slack",
  "arguments": {
    "question": "I need the exact URL for the production API, including the protocol (http/https) and port number."
  }
}

3. Acknowledge Tool (acknowledge_the_{role}_on_slack)

Purpose: Acknowledge receiving a reply from the human with a simple acknowledgment message.

When to use: If you called the ask tool and the human replied, then you MUST use this tool to acknowledge the reply. Do not use this tool if you have not called the ask tool before.

Parameters:

• acknowledgement (string): The text to tell the human to acknowledge receiving their reply. Keep it short.

Example:

{
  "tool": "acknowledge_the_boss_on_slack",
  "arguments": {
    "acknowledgement": "Thanks, got it!"
  }
}

Common acknowledgments: "Thanks", "Got it", "Understood", "Ok", "Will do", etc.

Tool Usage Workflow

The typical workflow for using these tools is:

1. Ask: Use the ask tool to ask your initial question

2. Clarify (if needed): If the human doesn't understand or asks back, use the clarify tool to re-ask more clearly

3. Acknowledge: Once you receive a helpful response, use the acknowledge tool to confirm you received their answer

This workflow ensures proper communication etiquette and helps maintain a good relationship with the human.

Development

Scripts

• bun run build - Build all TypeScript files

• bun run dev - Run with hot-reloading (no build required)

• bun run start - Run built code

• bun test - Run tests with Bun's test runner

• bun run test:ci - Run tests with coverage

• bun run clean - Clean build artifacts

Project Structure

src/
├── cli.ts                    # CLI entry point with sade
├── stdio.ts                  # Stdio MCP server implementation
├── serve.ts                  # HTTP MCP server implementation
├── human.ts                  # Abstract Human interface
├── slack-http-client.ts      # HTTP-based Slack implementation
├── slack-client.ts           # Slack client utilities
├── logger.ts                 # Logging utilities
└── types.ts                  # TypeScript type definitions

bin/
└── ask-on-slack              # Executable wrapper with fallback

dist/                         # Built files (generated)
├── cli.js                    # Built CLI
├── stdio.js                  # Built stdio server
└── serve.js                  # Built HTTP server

Smart Fallback

The bin/ask-on-slack file includes intelligent fallback behavior:

• Primary: Uses dist/cli.js if it exists (built version)

• Fallback: Uses src/cli.ts if built version doesn't exist (source version)

• No build step required: You can run the CLI directly from source

Testing

bun test              # Run tests in watch mode
bun run test:ci       # Run tests once with coverage

Logging

Log Levels

• DEBUG - Detailed debugging information

• INFO - General information (default)

• WARN - Warning messages

• ERROR - Error messages

Log Output

• Without --log-file: All log messages are written to stderr (default behavior)

• With --log-file: All log messages are written to the specified file instead of stderr

Example with Logging

# Log to a file with debug level
bunx @rodrigolive/ask-on-slack stdio \
  --slack-bot-token "xoxb-your-token" \
  --slack-app-token "xapp-your-token" \
  --slack-channel-id "C1234567890" \
  --slack-user-id "U1234567890" \
  --log-file "/tmp/ask-on-slack.log" \
  --log-level "DEBUG"

Troubleshooting

Common Issues

1. Connection Issues

   • Verify all tokens are correct

   • Check that the bot is invited to the channel

   • Ensure bot has required scopes: chat:write, channels:read, users:read

2. No Response Received

   • Verify the user ID is correct (format: U1234567890)

   • Ensure the user responds in the message thread

   • Check that the bot has permission to read messages in the channel

3. Authentication Errors

   • Bot token should start with xoxb-

   • App token should start with xapp-

   • Regenerate tokens if needed

4. Build Issues

   • The CLI works without build step (fallback to source)

   • Use DEBUG=1 to see which CLI is being used

   • Run bun run build to create optimized dist files

Debug Mode

Enable debug output to see which CLI is being used:

DEBUG=1 bunx @rodrigolive/ask-on-slack --version
# Output: Using CLI: /path/to/dist/cli.js (or src/cli.ts)

License

MIT