SQL Assistant MCP Server

Connects Claude to a Microsoft SQL Server database over stdio. Ask Claude to query your database, inspect table structures, or preview execution plans — without leaving the chat.

Installation

pip install sql-mcp-server

You also need the ODBC Driver for SQL Server:
https://learn.microsoft.com/en-us/sql/connect/odbc/download-odbc-driver-for-sql-server

Tools

list_tables : Lists all user-created tables, grouped by schema.

describe_table : Shows columns, data types, nullability, and defaults for a table.

run_query : Runs a SELECT query and returns results. Write operations (INSERT, UPDATE, DELETE, DROP, etc.) are blocked.

explain_query : Returns SQL Server's estimated execution plan via SET SHOWPLAN_TEXT. Good to run before a slow or unfamiliar query.

get_table_sample : Returns the first N rows from a table (max 20, default 5). Pass rows=10 for more.

Project Structure

sql-mcp-server/
├── server.py          # MCP server and tool definitions
├── db.py              # SQL Server connection helper (loads .env)
├── pyproject.toml     # Project metadata and dependencies
├── uv.lock            # Locked dependency versions (uv)
├── .env               # Connection config (not committed)
└── README.md

Setup

1. Configure the database connection

Create a .env file in the project root:

Windows Authentication:

DB_DRIVER=ODBC Driver 17 for SQL Server
DB_SERVER=YOUR_SERVER_NAME\SQLEXPRESS
DB_NAME=your_database_name

SQL Server Authentication:

DB_DRIVER=ODBC Driver 17 for SQL Server
DB_SERVER=YOUR_SERVER_NAME\SQLEXPRESS
DB_NAME=your_database_name
DB_USER=your_username
DB_PASSWORD=your_password

If you're using the Claude Desktop config below, put credentials in the env block — no .env file needed.

2. Register with Claude Desktop

Add this to claude_desktop_config.json — usually at %APPDATA%\Claude\claude_desktop_config.json on Windows.

Method 1 — Installed from PyPI (Recommended)

Windows Authentication:

{
  "mcpServers": {
    "sql-assistant": {
      "command": "sql-mcp-server",
      "args": [],
      "env": {
        "DB_SERVER": "YOUR_SERVER_NAME\\\\SQLEXPRESS",
        "DB_NAME": "your_database_name",
        "DB_DRIVER": "ODBC Driver 17 for SQL Server"
      }
    }
  }
}

SQL Server Authentication:

{
  "mcpServers": {
    "sql-assistant": {
      "command": "sql-mcp-server",
      "args": [],
      "env": {
        "DB_SERVER": "YOUR_SERVER_NAME\\\\SQLEXPRESS",
        "DB_NAME": "your_database_name",
        "DB_DRIVER": "ODBC Driver 17 for SQL Server",
        "DB_USER": "your_username",
        "DB_PASSWORD": "your_password"
      }
    }
  }
}

Method 2 — Run with uvx (no install)

{
  "mcpServers": {
    "sql-assistant": {
      "command": "uvx",
      "args": ["sql-mcp-server"],
      "env": {
        "DB_SERVER": "YOUR_SERVER_NAME\\\\SQLEXPRESS",
        "DB_NAME": "your_database_name",
        "DB_DRIVER": "ODBC Driver 17 for SQL Server",
        "DB_USER": "your_username",
        "DB_PASSWORD": "your_password"
      }
    }
  }
}

Method 3 — Local Installation (For Development)

If you cloned the repository and want to run it from source, use uv and specify the absolute path to your project directory.

Windows Authentication:

{
  "mcpServers": {
    "sql-assistant": {
      "command": "uv",
      "args": [
        "--directory",
        "C:/path/to/sql-mcp-server",
        "run",
        "server.py"
      ],
      "env": {
        "DB_SERVER": "YOUR_SERVER_NAME\\\\SQLEXPRESS",
        "DB_NAME": "your_database_name",
        "DB_DRIVER": "ODBC Driver 17 for SQL Server"
      }
    }
  }
}

SQL Server Authentication:

{
  "mcpServers": {
    "sql-assistant": {
      "command": "uv",
      "args": [
        "--directory",
        "C:/path/to/sql-mcp-server",
        "run",
        "server.py"
      ],
      "env": {
        "DB_SERVER": "YOUR_SERVER_NAME\\\\SQLEXPRESS",
        "DB_NAME": "your_database_name",
        "DB_DRIVER": "ODBC Driver 17 for SQL Server",
        "DB_USER": "your_username",
        "DB_PASSWORD": "your_password"
      }
    }
  }
}

Replace C:/path/to/sql-mcp-server with the actual path to your cloned repo.

Replace all placeholder values with your actual credentials. Restart Claude Desktop after saving.

Usage

With the server connected, try asking Claude:

• "What tables are in the database?"
• "Describe the Orders table."
• "Show me 10 rows from Customers."
• "Run: SELECT TOP 5 * FROM Sales.Orders WHERE Status = 'Pending'"
• "Explain this query: SELECT * FROM Products WHERE Price > 100"

Safety

Only SELECT queries run. These keywords are blocked before reaching the database:

INSERT UPDATE DELETE DROP TRUNCATE ALTER CREATE EXEC

Table and schema names are validated against injection patterns. Results are capped at 200 rows.

⚠️ Don't commit your .env file — it contains your connection credentials.

Requirements

• Python 3.10+
• SQL Server with ODBC Driver 17 or 18
• Claude Desktop with MCP support

License

MIT