Five Whys MCP Server

A stateful MCP server that guides AI models through the 5-Whys root cause analysis technique.

Features

• Stateful Sessions: Maintains conversation state using session IDs
• Automatic Cleanup: Automatically removes old sessions (30-minute timeout, max 100 sessions)
• Simple API: Just provide a session ID to continue where you left off
• No History Management: The server handles all history internally

Installation

yarn install

Usage

Starting a New Session

To start a new 5-Whys analysis:

{
  "name": "five_whys",
  "arguments": {
    "problem": "Customer complaints are increasing",
    "needsMoreWhys": true
  }
}

The server will return a session ID and the first "why" question:

{
  "content": [{"type": "text", "text": "Why does the problem \"Customer complaints are increasing\" occur?"}],
  "state": {
    "sessionId": "session_1703123456789_abc123def",
    "needsMoreWhys": true
  }
}

Continuing a Session

To continue with the next "why" question, use the session ID:

{
  "name": "five_whys",
  "arguments": {
    "sessionId": "session_1703123456789_abc123def",
    "currentReason": "Our response time is too slow",
    "needsMoreWhys": true
  }
}

Completing the Analysis

When you want to finish the analysis, set needsMoreWhys to false:

{
  "name": "five_whys",
  "arguments": {
    "sessionId": "session_1703123456789_abc123def",
    "currentReason": "We don't have enough staff",
    "needsMoreWhys": false
  }
}

The server will return a complete summary with the root cause.

Session Management

• Session IDs: Automatically generated when starting a new session (format: session_${timestamp}_${randomString})
• Timeout: Sessions expire after 30 minutes of inactivity
• Capacity: Maximum 100 concurrent sessions
• Cleanup: Old sessions are automatically removed when capacity is reached

API Schema

Input Schema

{
  sessionId?: string;        // Optional: Session ID to continue existing session
  problem?: string;          // Required for new sessions: The problem to analyze
  currentReason?: string;    // Optional: Answer to the current "why" question
  needsMoreWhys?: boolean;   // Optional: Whether to continue asking "why" (defaults to true if not provided)
}

Output

The server returns:

• content: The next question or final summary
• state: Contains the session ID for the next call

Development

# Install dependencies
yarn install

# Run in development mode (requires tsx)
yarn dev

# Build for production
yarn build

# Run built version
yarn start

Example Workflow

• Start: Provide a problem → Get session ID and first question
• Continue: Provide session ID + answer → Get next question
• Repeat: Continue until you have 5 answers or want to stop
• Finish: Provide session ID + final answer + needsMoreWhys: false → Get summary

The server handles all the complexity of maintaining the conversation state and history.