MSSQL MCP Server

A Model Context Protocol (MCP) server for Microsoft SQL Server databases, providing secure database operations through a standardized interface.

Note: This project was created from the Azure SQL AI Samples repository, specifically the MssqlMcp/Node implementation. The upstream sample was removed from that repository in June 2026 (PR #96, "Removed unsafe MCP sample"); this fork includes all upstream changes through the final version (Nov 2025), including the SELECT ... INTO security fix.

Features

• Secure Database Operations: Execute SELECT queries with comprehensive security validation

• Table Management: List, describe, and manage database tables and indexes

• Data Manipulation: Insert, update, and query data with proper validation

• Read-Only Mode: Optional read-only mode for enhanced security

• Connection Pooling: Efficient database connection management with retry logic

• SQL Injection Protection: Advanced security measures to prevent malicious queries

Related MCP server: Microsoft SQL Server MCP Server

Available Tools

Read Operations (Always Available)

• list_table - List tables in the database, optionally filtered by schema

• read_data - Execute SELECT queries with security validation

• describe_table - Get table schema information

• describe_index - Get index information for tables

Write Operations (Requires READONLY=false)

• insert_data - Insert data into tables

• update_data - Update existing records

• create_table - Create new tables

• create_index - Create indexes on tables

• drop_table - Drop tables (use with caution)

Installation

1. Clone this repository:

git clone <repository-url>
cd mcp-server-mssql

2. Install dependencies:

npm install

3. Build the project:

npm run build

Configuration

Environment Variables

The server supports both individual environment variables and a DATABASE_URL format:

Option 1: Individual Variables

SERVER_NAME=your-server.database.windows.net
DATABASE_NAME=your-database
SQL_USER=your-username
SQL_PASSWORD=your-password
READONLY=true
TRUST_SERVER_CERTIFICATE=true
CONNECTION_TIMEOUT=30

Option 2: DATABASE_URL Format

DATABASE_URL=mssql://username:password@server:1433/database
READONLY=true
TRUST_SERVER_CERTIFICATE=true

Configuration Parameters

*Either individual variables or DATABASE_URL is required.

Usage

As an MCP Server

Configure the server in your MCP client (e.g., Claude Desktop, Cursor):

{
  "mcpServers": {
    "mssql-server": {
      "command": "node",
      "args": ["/path/to/mcp-server-mssql/dist/index.js"],
      "env": {
        "DATABASE_URL": "mssql://username:password@server:1433/database",
        "READONLY": "true",
        "TRUST_SERVER_CERTIFICATE": "true"
      }
    }
  }
}

Example Configuration Files

See the included sample configurations:

• sql-auth-config-example.json - Basic configuration example

• sql-auth-config-individual.json - Individual environment variables example

Sample Configurations

Claude Desktop

{
  "mcpServers": {
    "mssql-sql-auth": {
      "command": "node",
      "args": ["/path/to/mcp-server-mssql/dist/index.js"],
      "env": {
        "DATABASE_URL": "mssql://your-username:your-password@your-server:1433/your-database",
        "READONLY": "false",
        "TRUST_SERVER_CERTIFICATE": "true"
      }
    }
  }
}

Cursor

{
  "mcpServers": {
    "mssql-sql-auth": {
      "command": "node",
      "args": ["/path/to/mcp-server-mssql/dist/index.js"],
      "env": {
        "DATABASE_URL": "mssql://your-username:your-password@your-server:1433/your-database",
        "READONLY": "false",
        "TRUST_SERVER_CERTIFICATE": "true"
      }
    }
  }
}

Security Features

Query Validation

• Only SELECT queries are allowed in read operations

• Comprehensive SQL injection protection

• Dangerous keyword detection

• Pattern-based malicious query detection

• Query length limits

Connection Security

• Encrypted connections by default

• Configurable certificate trust

• Connection pooling with timeout management

• Automatic retry logic with exponential backoff

Read-Only Mode

When READONLY=true:

• Only read operations are available

• NOLOCK hints are automatically added to queries

• Write operations are completely disabled

Development

Project Structure

src/
├── index.ts              # Main server implementation
├── tools/                # Tool implementations
│   ├── CreateIndexTool.ts
│   ├── CreateTableTool.ts
│   ├── DescribeIndexTool.ts
│   ├── DescribeTableTool.ts
│   ├── DropTableTool.ts
│   ├── InsertDataTool.ts
│   ├── ListTableTool.ts
│   ├── ReadDataTool.ts
│   └── UpdateDataTool.ts
└── samples/              # Configuration examples
    ├── claude_desktop_config.json
    ├── cursor_desktop_config.json
    └── vscode_agent_config.json

Building

npm run build

Development Mode

npm run watch

Testing

npm start

Error Handling

The server provides comprehensive error handling:

• Connection errors with retry logic

• Query validation errors

• Permission errors

• Timeout handling

• Graceful shutdown on process termination

Contributing

This project is based on the Azure SQL AI Samples repository. Contributions are welcome!

1. Fork the repository

2. Create a feature branch

3. Make your changes

4. Add tests if applicable

5. Submit a pull request

License

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

Acknowledgments

• Based on the Azure SQL AI Samples repository

• Built with the Model Context Protocol SDK

• Uses the mssql library for SQL Server connectivity

Support

For issues and questions:

1. Check the Azure SQL AI Samples repository for related issues

2. Create an issue in this repository

3. Review the Model Context Protocol documentation

Related Projects

• Azure SQL AI Samples - Original source repository

• Model Context Protocol - Protocol specification

• MCP TypeScript SDK - SDK used in this project