MCP Database Server (Node.js)

🌐 Language: English | Bahasa Indonesia

A Node.js & TypeScript MCP Server supporting Multi-Database (PostgreSQL & MySQL) environments with a Main Connection & Sub Connection (Dynamic Routing) architecture.

Replaces legacy setups that required multiple separate servers with a single unified server that is efficient, secure, and memory-friendly.

🌟 Key Features

1. Main Connection

   • Configure credentials once (host, port, user, password, ssl) for an entire database cluster / server.

2. Sub Connection

   • Register named databases hosted within that main server (e.g., db_app, db_analytics, db_store).

3. Dynamic Connection (Automatic Routing)

   • MCP Clients / AI Agents can flexibly target databases:

     • Using sub-connection alias IDs: connectionId: "db_app"

     • Composite format: connectionId: "postgres_main:my_database"

     • Or dynamically without prior registration: mainId: "postgres_main", database: "any_db_name"

4. Multiple Database Engines

   • Supports PostgreSQL (via pg.Pool)

   • Supports MySQL (via mysql2/promise)

   • Adapter-based architecture (DatabaseAdapter), easily extensible to other engines (SQLite, MSSQL, etc.).

5. Connection Pool Caching

   • Connection pools are created lazily (on-demand) per database and cached for optimal performance without connection leaks.

6. Write Rules & Exceptions (Data Mutation Security)

   • Tiered write permissions: block mutations (allowWrite: false) with granular exceptions for specific operations (e.g., allow only INSERT & UPDATE).

Related MCP server: Database MCP Server

🛠️ Available MCP Tools

📦 Installation & Setup

Prerequisites

Ensure your environment meets the minimum requirements:

• Node.js: >= 18.0.0

• npm: >= 9.0.0

• Access to a PostgreSQL and/or MySQL database server.

Method 1: Download Pre-built Release (Recommended)

Pre-built releases come with pre-compiled JavaScript (dist/), requiring no TypeScript compiler or devDependencies.

1. Download & Extract Download the latest release archive (.tar.gz or .zip) from GitHub Releases:

   • Linux / macOS / Git Bash:

     mkdir -p mcp_database && cd mcp_database
     # Extract the downloaded archive into the directory:
     tar -xzf /path/to/mcp-database-server-*.tar.gz

   • Windows (PowerShell):

     Expand-Archive -Path .\mcp-database-server-*.zip -DestinationPath .\mcp_database
     cd mcp_database

2. Install Production Dependencies Install only runtime dependencies without development packages:

   npm install --omit=dev

3. Setup Configuration Copy the example configuration file to create your local connections.json:

   # Linux / macOS / Git Bash:
   cp connections.example.json connections.json
   
   # Windows Command Prompt / PowerShell:
   copy connections.example.json connections.json

   (Optional) Copy .env.example if using environment variables:

   # Linux / macOS / Git Bash:
   cp .env.example .env
   
   # Windows Command Prompt / PowerShell:
   copy .env.example .env

4. (Optional) Global CLI Linking To make the mcp-database command directly accessible anywhere on your system:

   npm link

Method 2: Install from Source (Manual / Development)

Use this method if you want to contribute, modify source files, or run the bleeding-edge version directly from the repository.

1. Clone Repository & Install Dependencies

   git clone https://github.com/RifkyR3/mcp_database.git
   cd mcp_database
   npm install

2. Build the Project Compile TypeScript source files into production-ready JavaScript (dist/):

   npm run build

   Tip: You can also run the server directly in development mode without compiling by using npm run dev.

3. Setup Configuration

   # Linux / macOS / Git Bash:
   cp connections.example.json connections.json
   
   # Windows Command Prompt / PowerShell:
   copy connections.example.json connections.json

   (Optional) Copy .env.example:

   # Linux / macOS / Git Bash:
   cp .env.example .env
   
   # Windows Command Prompt / PowerShell:
   copy .env.example .env

4. (Optional) Global CLI Linking

   npm link

📁 Configuration Structure (connections.json)

Copy connections.example.json to connections.json and customize it with your database credentials:

{
  "connections": {
    "postgres_main": {
      "id": "postgres_main",
      "engine": "postgres",
      "host": "localhost",
      "port": 5432,
      "user": "your_pg_user",
      "password": "your_pg_password",
      "defaultDatabase": "postgres",
      "description": "Primary PostgreSQL Server",
      "allowWrite": false,
      "writeExceptions": ["INSERT", "UPDATE"],
      "subConnections": [
        { 
          "id": "app_db", 
          "database": "my_application_db", 
          "description": "Main Application Database" 
        },
        { 
          "id": "analytics_db", 
          "database": "my_analytics_db", 
          "description": "Analytics Database (Read Only)",
          "allowWrite": false,
          "writeExceptions": []
        }
      ]
    },
    "mysql_cluster": {
      "id": "mysql_cluster",
      "engine": "mysql",
      "host": "localhost",
      "port": 3306,
      "user": "your_mysql_user",
      "password": "your_mysql_password",
      "defaultDatabase": "information_schema",
      "description": "MySQL Cluster Server",
      "subConnections": [
        { 
          "id": "store_db", 
          "database": "ecommerce_db", 
          "description": "E-commerce Database" 
        }
      ]
    }
  }
}

Security Note: connections.json and mcp_config.json are excluded in .gitignore to prevent passwords and credentials from leaking publicly.

🚀 MCP Client Integration

In your MCP client configuration file (e.g., mcp_config.json, Claude Desktop config, or Antigravity config), add the server configuration:

{
  "mcpServers": {
    "mcp_database": {
      "command": "node",
      "args": [
        "/path/to/mcp_database/dist/index.js"
      ],
      "env": {
        "MCP_DB_CONFIG_PATH": "/path/to/mcp_database/connections.json"
      }
    }
  }
}

Or if linked globally via npm link:

{
  "mcpServers": {
    "mcp_database": {
      "command": "mcp-database",
      "env": {
        "MCP_DB_CONFIG_PATH": "/path/to/mcp_database/connections.json"
      }
    }
  }
}

Or using development mode with tsx:

{
  "mcpServers": {
    "mcp_database": {
      "command": "npx",
      "args": [
        "-y",
        "tsx",
        "/path/to/mcp_database/src/index.ts"
      ],
      "env": {
        "MCP_DB_CONFIG_PATH": "/path/to/mcp_database/connections.json"
      }
    }
  }
}

🎯 Restricting Specific Databases from MCP Client

If connections.json contains multiple databases, but you only want to expose specific ones (e.g., only app_db and store_db), you can add CLI arguments or environment variables in your client configuration:

Method 1: Using the args Parameter (Recommended)

{
  "mcpServers": {
    "mcp_database": {
      "command": "node",
      "args": [
        "/path/to/mcp_database/dist/index.js",
        "--databases=app_db,store_db"
      ],
      "env": {
        "MCP_DB_CONFIG_PATH": "/path/to/mcp_database/connections.json"
      }
    }
  }
}

Method 2: Using the ALLOWED_DATABASES Environment Variable

{
  "mcpServers": {
    "mcp_database": {
      "command": "node",
      "args": [
        "/path/to/mcp_database/dist/index.js"
      ],
      "env": {
        "MCP_DB_CONFIG_PATH": "/path/to/mcp_database/connections.json",
        "ALLOWED_DATABASES": "app_db,store_db"
      }
    }
  }
}

Benefits of filtering:

• All tools and actions (e.g. db_list_connections, db_discover_databases) only list and expose permitted databases, saving context window tokens and preventing information leakage.

• Database servers without any permitted databases are automatically hidden.

• Other databases outside the allowed list are strictly protected: query execution, dynamic registration, and discovery are rejected.

• Corresponding main connection credentials are still automatically resolved.

🔒 Write Rules & Write Exceptions (Database Mutation Protection)

This feature allows you to configure data mutation permissions (allowWrite) and SQL operation exceptions (writeExceptions).

💡 How It Works:

• allowWrite: false (write = false): All SQL mutation operations (INSERT, UPDATE, DELETE, DROP, TRUNCATE, ALTER, etc.) will be BLOCKED. Read queries (SELECT, SHOW, DESCRIBE, EXPLAIN) remain ALLOWED.

• writeExceptions: ["INSERT", "UPDATE"] (Exceptions): When allowWrite: false, operations specified in the exceptions list (e.g. INSERT and UPDATE) are STILL ALLOWED, while destructive operations like DELETE, DROP, TRUNCATE, ALTER remain BLOCKED.

• Conversely, if allowWrite: true (default), you can set writeExceptions: ["DROP", "TRUNCATE"] to selectively block those dangerous operations.

⚙️ How to Configure Write Rules

Rules can be configured across 3 hierarchical levels (priority order: Sub-Connection > Main Connection > Global):

1. Sub-Connection Level (Per Database in connections.json)

{
  "id": "app_db",
  "database": "my_application_db",
  "allowWrite": false,
  "writeExceptions": ["INSERT", "UPDATE"]
}

(Only the app_db database enforces this rule: INSERT & UPDATE allowed, DELETE & DROP blocked).

2. Main Connection Level (Per Host Server in connections.json)

{
  "postgres_main": {
    "id": "postgres_main",
    "engine": "postgres",
    "host": "localhost",
    "port": 5432,
    "user": "your_user",
    "password": "your_password",
    "allowWrite": false,
    "writeExceptions": ["INSERT", "UPDATE"]
  }
}

3. Global Level (in mcp_config.json)

Can be configured directly in mcp_config.json via CLI arguments:

{
  "mcpServers": {
    "mcp_database": {
      "command": "node",
      "args": [
        "/path/to/mcp_database/dist/index.js",
        "--databases=app_db,store_db",
        "--write=false",
        "--write-exceptions=INSERT,UPDATE"
      ],
      "env": {
        "MCP_DB_CONFIG_PATH": "/path/to/mcp_database/connections.json"
      }
    }
  }
}

🔄 Automated Database Crawl & Synchronization

You can crawl all databases on host servers and update connections.json automatically using two methods:

1. Via Terminal / CLI

# Sync all main connections
npm run sync

# Or sync a specific main connection
npm run sync postgres_main
npm run sync mysql_cluster

2. Via MCP Tool

Invoke the db_sync_databases tool from your MCP client / AI Agent with parameters:

{
  "mainId": "all",
  "removeMissing": false
}

📋 Inspect Connections & Filtering (db_list_connections)

You can inspect all configured connections, active pools, and test ALLOWED_DATABASES filter rules directly:

1. Via Terminal / CLI

# Beautiful formatted console summary
npm run list

# Test with database filter flag
npm run list -- --databases=app_db,store_db

# Output exact JSON (identical to db_list_connections MCP tool)
npm run list -- --json

2. Via MCP Tool

Call db_list_connections from your AI Agent / MCP client.

🧪 Testing & Verification

This project includes test scripts:

# 1. Test database connectivity
npm test

# 2. Test Write Rules & Write Exceptions
npm run test:write

📄 License

MIT License