MCP Database Server

A Model Context Protocol (MCP) server that provides safe, read-only database access to Large Language Models (LLMs). This enables LLMs like Claude to explore database schemas, sample data, and execute SELECT queries through a standardized interface.

⚠️ Early Development Notice: This project is in early development. While functional, it lacks comprehensive testing and production-ready features. Use at your own risk in production environments.

Features

• Schema Exploration: Discover database structure, tables, and columns
• Data Sampling: Preview table contents with configurable row limits
• Safe Querying: Execute read-only SELECT queries with built-in safety measures
• Multi-Database Support: PostgreSQL, MySQL, and SQLite
• MCP Protocol: Seamless integration with Claude Desktop and other MCP-compatible clients

Installation

Prerequisites

• Go 1.24.4 or higher
• Docker (for development database)
• One of the supported databases:
  • PostgreSQL
  • MySQL
  • SQLite

Quick Start

1. Clone the repository:

git clone https://github.com/melkeydev/mcp-database
cd mcp-database

2. Start the development database (PostgreSQL):

docker-compose up -d

3. Configure your database connection in config.yaml:

database:
  type: "postgres" # Options: postgres, mysql, sqlite
  connection_string: "postgres://postgres:postgres@localhost:5432/mcp_db?sslmode=disable"
  file: "database.db" # For SQLite only

4. Build and run:

go build -o mcp-database
./mcp-database -config config.yaml

Usage with Claude Desktop

Add the server to your Claude Desktop configuration:

macOS: ~/Library/Application Support/Claude/claude_desktop_config.json

Windows: %APPDATA%/Claude/claude_desktop_config.json

{
  "mcpServers": {
    "database": {
      "command": "/path/to/mcp-database",
      "args": ["-config", "/path/to/config.yaml"]
    }
  }
}

Available Tools

The server exposes three MCP tools:

1. scan_database

Discovers the database schema including all tables, columns, and their types.

// No parameters required

2. sample_table

Returns a sample of rows from a specified table.

{
  "table_name": "users",  // Required
  "limit": 10            // Optional, default: 10
}

3. query_database

Executes a read-only SELECT query.

{
  "query": "SELECT name, email FROM users WHERE created_at > '2024-01-01'"
}

Configuration

The config.yaml file supports the following database configurations:

PostgreSQL

database:
  type: "postgres"
  connection_string: "postgres://user:password@host:port/dbname?sslmode=disable"

MySQL

database:
  type: "mysql"
  connection_string: "user:password@tcp(host:port)/dbname"

SQLite

database:
  type: "sqlite"
  file: "path/to/database.db"

Architecture

mcp-database/
├── main.go              # Entry point
├── config/              # Configuration management
├── databases/           # Database connectors
│   ├── connector.go     # Common interface
│   ├── postgres/        # PostgreSQL implementation
│   ├── mysql/          # MySQL implementation
│   └── sqlite/         # SQLite implementation
├── handlers/           # Request handlers
├── mcp/               # MCP protocol implementation
└── types/             # Shared type definitions

Safety Features

• Read-only operations: All database operations are executed within read-only transactions
• Query validation: Only SELECT statements are allowed
• Resource limits: Configurable row limits for data sampling
• Error handling: Comprehensive error handling and reporting

Development

Building from Source

# Install dependencies
go mod download

# Build
go build -o mcp-database

# Run tests (coming soon)
go test ./...

Adding a New Database

1. Create a new package under databases/
2. Implement the DatabaseConnector interface
3. Update GetConnector() in databases/connector.go
4. Add configuration support in config/

Roadmap

• Comprehensive test suite
• Connection pooling
• Query result caching
• Support for more databases (Oracle, SQL Server)
• Query timeout configuration
• Result size limits
• Schema caching for better performance
• Support for custom SQL functions
• Docker image for easier deployment

Contributing

Contributions are welcome! Please feel free to submit a Pull Request. Since this is an early-stage project, please open an issue first to discuss major changes.

Areas where help is needed:

• Writing comprehensive tests
• Adding support for more databases
• Improving error messages and debugging
• Documentation improvements
• Performance optimizations

License

MIT License

Disclaimer

This project is in early development and not yet production-ready. While it implements safety measures for read-only access, please use caution when connecting to production databases. Always use appropriate credentials with minimal required permissions.

Acknowledgments

Built on the Model Context Protocol by Anthropic.