Mssql MCP Server by RichardHan

Microsoft SQL Server MCP Server

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A Model Context Protocol (MCP) server for secure SQL Server database access through Claude Desktop.

Features

• 🔍 List database tables
• 📊 Execute SQL queries (read-only by default; optional write mode)
• 🔐 Multiple authentication methods (SQL, Windows, Azure AD)
• 🏢 LocalDB and Azure SQL support
• 🔌 Custom port configuration

Quick Start

Install with Claude Desktop

Add to your claude_desktop_config.json:

{
  "mcpServers": {
    "mssql": {
      "command": "uvx",
      "args": ["--from", "microsoft-sql-server-mcp", "mssql_mcp_server"],
      "env": {
        "MSSQL_SERVER": "localhost",
        "MSSQL_DATABASE": "your_database",
        "MSSQL_USER": "your_username",
        "MSSQL_PASSWORD": "your_password"
      }
    }
  }
}

Configuration

Basic SQL Authentication

MSSQL_SERVER=localhost          # Required
MSSQL_DATABASE=your_database    # Required
MSSQL_USER=your_username        # Required for SQL auth
MSSQL_PASSWORD=your_password    # Required for SQL auth

Windows Authentication

MSSQL_SERVER=localhost
MSSQL_DATABASE=your_database
MSSQL_WINDOWS_AUTH=true         # Use Windows credentials

Azure SQL Database

MSSQL_SERVER=your-server.database.windows.net
MSSQL_DATABASE=your_database
MSSQL_USER=your_username
MSSQL_PASSWORD=your_password
# Encryption is automatic for Azure

Optional Settings

MSSQL_PORT=1433                 # Custom port (default: 1433)
MSSQL_ENCRYPT=true              # Force encryption (uses pymssql `encryption=require`)
MSSQL_TRUST_SERVER_CERTIFICATE=true  # Trust SQL Server TLS cert (default: true for non-Azure encrypt, false for Azure)
MSSQL_QUERY_TIMEOUT=300         # Query timeout in seconds (default: 300). Queries exceeding this limit are automatically terminated.
MSSQL_ALLOW_WRITES=1            # Allow INSERT/UPDATE/DELETE; tool name becomes execute_sql (default: read-only `query` tool)
MSSQL_COMMAND=query             # Optional override for the MCP tool name

Read-only vs write mode

By default the server exposes a query tool that only accepts a single read-only SELECT / WITH / set-operation statement (parsed as T-SQL) and sets readOnlyHint (so Cursor Ask mode can use it). Stacked batches (SELECT …; INSERT …), SELECT INTO, EXEC, and other non-SELECT statements are rejected before they reach the database driver.

Set MSSQL_ALLOW_WRITES=1 to expose execute_sql and allow writes. Prefer a least-privilege read-only SQL login for the default mode — the parser is fail-closed defense in depth, not a substitute for database permissions, and does not claim to prove arbitrary T-SQL is free of side effects.

Alternative Installation Methods

Using pip

pip install microsoft_sql_server_mcp

Then in claude_desktop_config.json:

{
  "mcpServers": {
    "mssql": {
      "command": "python",
      "args": ["-m", "mssql_mcp_server"],
      "env": { ... }
    }
  }
}

Development

git clone https://github.com/RichardHan/mssql_mcp_server.git
cd mssql_mcp_server
pip install -e .

Dependency notes

The mcp SDK is pinned to >=1.0.0,<2.0.0 in both pyproject.toml and requirements.txt.

mcp 2.0.0 removed the legacy Server decorator API (@app.list_resources(), @app.list_tools(), ...) that src/mssql_mcp_server/server.py is built on, so an unconstrained install crashes at import time with:

AttributeError: 'Server' object has no attribute 'list_resources'

This matters most for uvx --from git+... launches, which resolve dependencies fresh on every cold start and ignore uv.lock. Do not drop the upper bound until the server is migrated to the 2.x API.

Security

• Create a dedicated SQL user with minimal permissions (e.g. db_datareader for read-only deployments)
• Never use admin/sa accounts for the MCP connection
• Use Windows Authentication when possible
• Enable encryption for sensitive data
• Treat MSSQL_ALLOW_WRITES as an explicit opt-in; keep it off unless the user deliberately wants writes
• Read-only mode parses T-SQL and fail-closes on unsupported/stacked statements — still pair it with least-privilege DB grants

License

MIT