nowgnuesLee/mcp-host-api-server

MCP Host Server

An Express-based MCP (Model Context Protocol) host server that uses OpenAI's function calls to invoke MCP server tools and generate responses.

Features

• Express-based REST API server
• AI response generation through OpenAI API
• MCP server communication and tool invocation support
• Session-based conversation history management (in-memory storage)
• Google Calendar MCP server integration

Project Structure

src/
├── index.ts              # Main server application
├── MCP.ts               # MCP server connection and tool invocation management
├── config.ts            # Configuration file loading and environment variable management
├── types.ts             # TypeScript type definitions
└── middleware/
    └── validation.ts    # Request validation middleware

Configuration Files

config.json

Defines MCP server configuration.

{
  "mcp": {
    "servers": [
      {
        "name": "google-calendar",
        "command": "npx",
        "args": ["@cocal/google-calendar-mcp"],
        "env": {
          "GOOGLE_OAUTH_CREDENTIALS": "./google_auth.json"
        }
      }
    ]
  }
}

google_auth.json

Contains Google OAuth credentials. (Actual file is not included in repository for security reasons)

Environment Variables

Set the following variables in a .env file:

• OPEN_AI_KEY: OpenAI API key

API Endpoints

POST /api/chat

Process user messages and generate AI responses.

Request Body:

{
  "sessionId": "unique-session-id",
  "message": "User message",
  "tool": true // Whether to use tools (optional)
}

Response:

{
  "message": "AI response message"
}

POST /api/chat/clear

Clear conversation history for a specific session.

Request Body:

{
  "sessionId": "unique-session-id"
}

Response:

{
  "message": "Chat histories cleared",
  "sessionId": "unique-session-id"
}

GET /

Basic health check endpoint.

GET /api/health

Check server status.

Installation and Running

1. Install Dependencies

npm install

2. Set Environment Variables

Create a .env file and set the required environment variables:

OPEN_AI_KEY=your-openai-api-key

3. Google Authentication Setup

Place the google_auth.json file in the project root for Google Calendar API usage.

4. Run Development Server

npm run dev

Available Scripts

• npm run dev: Run development server (nodemon + ts-node)
• npm run lint: Run ESLint checks
• npm run lint:fix: Auto-fix ESLint issues
• npm run format: Format code with Prettier
• npm run format:check: Check Prettier formatting

Tech Stack

• Node.js: Runtime environment
• Express: Web framework
• TypeScript: Language for type safety
• OpenAI SDK: AI model API communication
• MCP SDK: Model Context Protocol implementation
• express-validator: Request validation
• dotenv: Environment variable management

Important Notes

• Currently uses in-memory storage for session information without a database
• All session data is reset when the server restarts
• Proper Google OAuth setup is required to use Google Calendar features

License

ISC