🚀 Bun Database MCP Server

A high-performance Model Context Protocol (MCP) server built with Bun and TypeScript, providing secure database operations for MySQL databases. This server enables AI assistants to safely interact with MySQL databases through a standardized protocol.

📹 Video Tutorials

Watch these comprehensive tutorials to understand MCP development:

✨ Features

• 🔌 Database Connection Management - Connect, disconnect, and check connection status
• 🔍 Safe Query Execution - Execute SELECT queries with parameterized statements
• 📝 CRUD Operations - Create, Read, Update, and Delete records securely
• 📊 Schema Inspection - Read database schema and table structures
• 🤖 MCP Prompts - Pre-built prompts for common database operations
• 📚 MCP Resources - Access database documentation and schema information
• 🛡️ SQL Injection Prevention - Built-in validation and sanitization
• ⚡ Built with Bun - Lightning-fast runtime and package management
• 🔒 Environment-based Configuration - Secure credential management

📋 Prerequisites

• Bun v1.0 or higher
• MySQL 5.7+ or MySQL 8.0+
• Node.js 18+ (for compatibility)

🛠️ Installation

1. Clone the repository:

git clone https://github.com/yourusername/bun-db-mcp.git
cd bun-db-mcp

2. Install dependencies:

bun install

3. Configure environment variables:

cp .env.example .env

Edit .env with your database credentials:

DB_HOST=localhost
DB_PORT=3306
DB_USER=your_user
DB_PASSWORD=your_password
DB_DATABASE=your_database

4. Initialize the database with sample data:

The repository includes an simple_import_employees.sql file with sample employee data. Import it using one of these methods.

Option 1: Using mysql command-line client:

mysql -u your_user -p your_database < simple_import_employees.sql

Option 2: From within MySQL client:

mysql -u your_user -p your_database

Then run:

source simple_import_employees.sql;

Option 3: Using mysqldump (for backup/restore):

# To export (backup)
mysqldump -u your_user -p your_database > backup.sql

# To import (restore)
mysql -u your_user -p your_database < backup.sql

🚀 Usage

Transport Options

The MCP server supports three different transport protocols:

1. STDIO Transport (Default)

Standard input/output communication for MCP clients like Claude Desktop:

bun run src/index.ts
# or
bun run src/index.ts --transport stdio

2. SSE Transport (Server-Sent Events)

HTTP-based transport using Server-Sent Events for real-time streaming:

bun run src/index.ts --transport sse --port 3000

• Endpoints:
  • GET http://localhost:3000/mcp - Establish SSE stream
  • POST http://localhost:3000/messages - Send JSON-RPC requests
• Session Management: Via sessionId query parameter

3. HTTP Transport (StreamableHTTP with OAuth)

Modern HTTP transport with OAuth authentication supporting both JSON and SSE responses:

bun run src/index.ts --transport http --port 3000 --oauth

• MCP Endpoint: GET/POST http://localhost:3000/mcp
• Auth Server: http://localhost:3001 (OAuth provider with demo flows)
• Session Management: Via Mcp-Session-Id header
• Authentication: Bearer token required in Authorization header
• Response Formats:
  • JSON: Accept: application/json, text/event-stream
  • SSE: Accept: text/event-stream, application/json

Authentication Flow:

1. OAuth server runs on port 3001 with demo authentication flows
2. Supports both in-memory demo provider and Google OAuth
3. MCP server validates Bearer tokens for protected resources
4. Set GOOGLE_CLIENT_ID and GOOGLE_CLIENT_SECRET environment variables for Google OAuth

Starting the Server

Run with default STDIO transport:

bun run start

Run with specific transport:

# SSE transport
bun run src/index.ts --transport sse --port 3000

# HTTP transport with OAuth
bun run src/index.ts --transport http --port 3000 --oauth

# HTTP transport without OAuth (not recommended)
bun run src/index.ts --transport http --port 3000

For development with auto-reload:

bun run dev

Available Tools

The server provides six powerful tools for database operations:

1. connection - Manage Database Connection

{
  "action": "connect" | "disconnect" | "status"
}

2. query - Execute SELECT Queries

{
  "sql": "SELECT * FROM employees WHERE hire_date > ?",
  "params": ["2000-01-01"]
}

3. create - Insert Records

{
  "table": "employees",
  "data": {
    "emp_no": 500000,
    "birth_date": "1990-05-15",
    "first_name": "John",
    "last_name": "Doe",
    "gender": "M",
    "hire_date": "2024-01-15"
  }
}

4. update - Update Records

{
  "table": "employees",
  "data": { "hire_date": "2024-02-01" },
  "where": { "emp_no": 500000 }
}

5. delete - Delete Records

{
  "table": "employees",
  "where": { "emp_no": 500000 }
}

6. readSchema - Inspect Database Schema

{
  "table": "employees"
}

Available Prompts

The server provides pre-built prompts for common database operations:

1. query-employees - Natural Language Queries

Query the employees table using natural language instructions.

• Arguments: instructions - e.g., "count female employees", "show 10 recent hires"

2. insert-employee - Add New Employee

Insert a new employee with all related information (department, title, salary).

• Arguments: employee_info - Employee details in natural language

3. delete-employee - Remove Employee

Delete an employee and all related records from the database.

• Arguments: employee_identifier - Employee number or name

4. manage-departments - Department Operations

Insert a new department or delete an existing department.

• Arguments: instructions - e.g., "add Marketing department", "delete department d005"

Available Resources

The server exposes the following MCP resources:

bun-db-mcp://general-database - Database Schema Documentation

• Type: text/markdown
• Description: Complete documentation of the employee database schema including:
  • Table structures and columns
  • Entity relationships
  • Key design patterns
  • Common query patterns
  • Mermaid ER diagram

🧪 Testing

Run the test suite:

bun test

Run specific test files:

bun test:db      # Database connection tests
bun test:tools   # Tool validation tests

Watch mode for development:

bun test:watch

🔧 Configuration

MCP Client Configuration

STDIO Transport (Claude Desktop)

To use with Claude Desktop or other MCP clients, add to your configuration:

{
  "mcpServers": {
    "bun-db-mcp": {
      "command": "bun",
      "args": [
        "run",
        "<root path>/src/index.ts",
        "--transport",
        "stdio"
      ],
      "env": {
        "DB_HOST": "127.0.0.1",
        "DB_PORT": "3306",
        "DB_USER": "root",
        "DB_PASSWORD": "<your_password>",
        "DB_DATABASE": "employees"
      }
    }
  }
}

HTTP/SSE Transport (Web Clients)

For HTTP-based transports, use curl or web clients:

SSE Transport Example:

# Establish SSE stream
curl -N -H "Accept: text/event-stream" \
  http://localhost:3000/mcp

# Send requests (in another terminal)
curl -X POST http://localhost:3000/messages?sessionId=<session-id> \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc": "2.0", "id": 1, "method": "tools/list"}'

HTTP Transport with OAuth Example:

# First, get an access token from the auth server
curl -X POST http://localhost:3001/oauth/token \
  -H "Content-Type: application/json" \
  -d '{"grant_type": "client_credentials", "client_id": "demo-client", "client_secret": "demo-secret"}'

# Use the token to make MCP requests
curl -X POST http://localhost:3000/mcp \
  -H "Content-Type: application/json" \
  -H "Accept: application/json, text/event-stream" \
  -H "Authorization: Bearer <access-token>" \
  -d '{"jsonrpc": "2.0", "id": 1, "method": "tools/list"}'

# SSE response with authentication
curl -X POST http://localhost:3000/mcp \
  -H "Content-Type: application/json" \
  -H "Accept: text/event-stream, application/json" \
  -H "Authorization: Bearer <access-token>" \
  -d '{"jsonrpc": "2.0", "id": 1, "method": "tools/list"}' \
  --no-buffer

Environment Variables

Variable	Description	Default
DB_HOST	MySQL host address	localhost
DB_PORT	MySQL port	3306
DB_USER	Database user	root
DB_PASSWORD	Database password	-
DB_DATABASE	Database name	mcp_test
GOOGLE_CLIENT_ID	Google OAuth client ID (optional)	-
GOOGLE_CLIENT_SECRET	Google OAuth client secret (optional)	-

🏗️ Project Structure

bun-db-mcp/
├── src/
│   ├── index.ts           # Main MCP server with transport selection
│   ├── handlers.ts        # Shared MCP request handlers
│   ├── transports/        # Transport implementations
│   │   ├── stdio.ts       # STDIO transport (default)
│   │   ├── sse.ts         # Server-Sent Events transport
│   │   └── http.ts        # StreamableHTTP transport with OAuth support
│   ├── auth/              # OAuth authentication providers
│   │   ├── demoInMemoryOAuthProvider.ts  # Demo OAuth provider
│   │   └── googleOAuthProvider.ts        # Google OAuth provider
│   ├── db/
│   │   ├── connection.ts  # Database connection manager
│   │   └── types.ts       # TypeScript type definitions
│   ├── tools/
│   │   └── index.ts       # Tool implementations
│   ├── specs/
│   │   ├── database-schema.md     # Database schema documentation
│   │   ├── query-employees.md     # Query prompt specification
│   │   ├── insert-employee-info.md # Insert prompt specification
│   │   ├── delete-employee.md     # Delete prompt specification
│   │   └── manage-departments.md  # Department management prompt
│   └── utils/
│       └── validation.ts  # Input validation & sanitization
├── tests/
│   ├── db.test.ts         # Database tests
│   └── tools.test.ts      # Tool tests
├── .env.example           # Environment template
└── package.json           # Project configuration

🔒 Security Features

• OAuth Authentication - Bearer token authentication for HTTP transport
• Protected Resources - Access control for sensitive database operations
• Parameterized Queries - All queries use prepared statements to prevent SQL injection
• Input Validation - Table and column names are validated against strict patterns
• Identifier Escaping - Database identifiers are properly escaped
• SELECT-only Queries - Query tool restricted to SELECT statements only
• Environment Variables - Sensitive credentials stored in environment files
• CORS Protection - Configurable cross-origin resource sharing policies

🤝 Contributing

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

1. Fork the repository
2. Create your feature branch (git checkout -b feature/AmazingFeature)
3. Commit your changes (git commit -m 'Add some AmazingFeature')
4. Push to the branch (git push origin feature/AmazingFeature)
5. Open a Pull Request

📄 License

This project is licensed under the MIT License - see the LICENSE file for details.

🙏 Acknowledgments

• Built with Bun - The fast all-in-one JavaScript runtime
• Uses MCP SDK for protocol implementation
• Database connectivity via mysql2

📊 Performance

Thanks to Bun's optimized runtime:

• 🚀 Fast Startup - Server starts in milliseconds
• ⚡ Low Memory - Efficient memory usage
• 🔥 High Throughput - Handle multiple database operations efficiently

🐛 Troubleshooting

Common Issues

1. Connection Refused

   • Verify MySQL is running
   • Check host and port in .env
   • Ensure user has proper permissions

2. Authentication Failed

   • Verify credentials in .env
   • Check MySQL user permissions
   • Ensure database exists

3. Module Not Found

   • Run bun install to install dependencies
   • Verify Bun version with bun --version

📞 Support

For issues and questions:

• Open an issue on GitHub Issues
• Check existing issues for solutions
• Provide detailed error messages and steps to reproduce

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Built with ❤️ using Bun and TypeScript