pyodbc MCP Server

A Model Context Protocol (MCP) server that provides read-only access to Microsoft SQL Server databases using Windows Authentication.

Built for environments where:

• 🔐 Windows Authentication is required (no username/password storage)
• 🛡️ Read-only access is mandated by IT security policy
• 🖥️ SQL Server is accessed from Windows workstations
• 🤖 AI assistants need safe database access (Claude Code, etc.)

Features

• Windows Authentication - Uses Trusted_Connection via pyodbc, no credentials to manage
• Read-only by design - Only SELECT queries allowed, dangerous keywords blocked
• Row limiting - Prevents accidental large result sets (configurable, max 1000)
• Schema exploration - List tables, views, describe columns, find relationships
• MCP compatible - Works with Claude Code, Claude Desktop, and any MCP client

Available Tools

Tool	Description
ListTables	List all tables in the database, optionally filtered by schema
ListViews	List all views in the database, optionally filtered by schema
DescribeTable	Get column definitions for a specific table
GetTableRelationships	Find foreign key relationships for a table
ReadData	Execute a SELECT query (with security filtering)

Installation

Prerequisites

• Python 3.10+
• Windows with ODBC Driver 17+ for SQL Server
• Network access to your SQL Server
• Windows domain account with SELECT permissions on target database

Install from PyPI

pip install pyodbc-mcp-server

Install from Source

git clone https://github.com/jjones-wps/pyodbc-mcp-server.git
cd pyodbc-mcp-server
pip install -e .

Install ODBC Driver (if needed)

Download and install Microsoft ODBC Driver 17 for SQL Server.

Configuration

Environment Variables

Variable	Default	Description
MSSQL_SERVER	localhost	SQL Server hostname or IP
MSSQL_DATABASE	master	Target database name
ODBC_DRIVER	ODBC Driver 17 for SQL Server	ODBC driver name

Claude Code Configuration

Add to your ~/.claude.json (or %USERPROFILE%\.claude.json on Windows):

{
  "mcpServers": {
    "mssql": {
      "type": "stdio",
      "command": "cmd",
      "args": ["/c", "python", "-m", "mssql_mcp_server"],
      "env": {
        "MSSQL_SERVER": "your-sql-server",
        "MSSQL_DATABASE": "your-database"
      }
    }
  }
}

Alternative: Direct script execution

{
  "mcpServers": {
    "mssql": {
      "type": "stdio",
      "command": "cmd",
      "args": [
        "/c",
        "python",
        "C:\\path\\to\\pyodbc-mcp-server\\src\\mssql_mcp_server\\server.py"
      ],
      "env": {
        "MSSQL_SERVER": "your-sql-server",
        "MSSQL_DATABASE": "your-database"
      }
    }
  }
}

Note for Windows users: The cmd /c wrapper is required for proper stdio communication with MCP clients on Windows.

Claude Desktop Configuration

Add to your Claude Desktop config (%APPDATA%\Claude\claude_desktop_config.json):

{
  "mcpServers": {
    "mssql": {
      "command": "python",
      "args": ["-m", "mssql_mcp_server"],
      "env": {
        "MSSQL_SERVER": "your-sql-server",
        "MSSQL_DATABASE": "your-database"
      }
    }
  }
}

Usage Examples

Once configured, you can ask Claude to:

Explore Schema

"List all tables in the dbo schema"
"Describe the structure of the customers table"
"What are the foreign key relationships for the orders table?"

Query Data

"Show me the first 10 rows from the products table"
"Find all orders from the last 30 days"
"What are the top 5 customers by total order value?"

Analyze Relationships

"Find all tables that reference the customer table"
"Show me the relationship between orders and order_lines"

Security

This server is designed with security as a primary concern:

Read-Only Enforcement

• Only queries starting with SELECT are allowed
• Dangerous keywords are blocked even in subqueries:
  • INSERT, UPDATE, DELETE, DROP, CREATE, ALTER
  • EXEC, EXECUTE, TRUNCATE, GRANT, REVOKE, DENY
  • BACKUP, RESTORE, SHUTDOWN, DBCC

Windows Authentication

• Uses Trusted_Connection=yes - no passwords stored or transmitted
• Leverages existing Windows domain security
• Your database permissions are enforced by SQL Server

Row Limiting

• Default limit: 100 rows per query
• Maximum limit: 1000 rows per query
• Prevents accidental retrieval of large datasets

Development

Running Tests

pip install -e ".[dev]"
pytest

Running Locally

# Set environment variables
export MSSQL_SERVER=your-server
export MSSQL_DATABASE=your-database

# Run the server
python -m mssql_mcp_server

Troubleshooting

"ODBC Driver not found"

Install the Microsoft ODBC Driver for SQL Server:

• Download ODBC Driver 17

"Login failed" or "Cannot connect"

1. Verify your Windows account has access to the SQL Server
2. Test connection with sqlcmd -S your-server -d your-database -E
3. Check firewall allows connection on port 1433

"Tools not appearing in Claude Code"

1. Ensure type: "stdio" is in your config
2. Use the cmd /c wrapper on Windows
3. Restart Claude Code after config changes
4. Check Claude Code logs for MCP errors

Contributing

Contributions are welcome! Please:

1. Fork the repository
2. Create a feature branch
3. Add tests for new functionality
4. Submit a pull request

License

MIT License - see LICENSE file.

Acknowledgments

• Built with FastMCP for MCP protocol handling
• Uses pyodbc for SQL Server connectivity
• Inspired by the need for safe AI access to enterprise databases

Related Projects

• MCP Specification
• Claude Code
• FastMCP