MS SQL MCP Connector

A Model Context Protocol (MCP) server that provides tools for interacting with MS SQL Server.

Features

• list_tables_and_views: List all tables and views.
• list_routines: List all stored procedures and functions.
• search_objects: Fuzzy search across all schema objects.
• get_object_definition: Fetch the SQL definition for routines or column info for tables.
• query_data: Secure SELECT-only tool.
  • Automatically enforces TOP 100.
  • Automatically injects WITH (NOLOCK).
  • Blocks DML/DDL (UPDATE, DELETE, etc.).
  • Supports parameterized queries.

Resources

• db://schema: Complete database schema overview as JSON.
• db://tables/{name}/schema: Schema definition for a specific table.

Prompts

• analyze-table: Analyze a table schema and suggest usage patterns.
• query-assistant: Get assistance in writing a T-SQL query based on the database schema.

LangChain Integration

This project is fully compatible with LangChain. You can consume these tools in a LangChain agent using the @langchain/mcp-adapters package.

Stdio Transport (Local)

import { McpTool } from "@langchain/mcp-adapters";

const tools = await McpTool.fromServer({
  name: "sql-server",
  stdio: {
    command: "node",
    args: ["dist/index.js", "stdio"],
    env: process.env // Ensure DB_ credentials are set
  }
});

Streamable HTTP Transport (SSE)

const tools = await McpTool.fromServer({
  name: "sql-server",
  sse: {
    url: "http://localhost:3000/mcp"
  }
});

See examples/langchain.ts for a full implementation.

Architecture

This project follows SRP (Single Responsibility Principle):

• DatabaseService: Handles all MS SQL database interactions.
• QuerySanitizer: Encapsulates security logic and query rewriting (NOLOCK, TOP 100).
• index.ts: MCP Server orchestration and transport management.

Transport Modes

1. Stdio (Local/CLI)

Default mode used by most MCP clients (e.g., Claude Desktop, MCP Inspector).

npm start stdio

2. Streamable HTTP (SSE)

Exposes the MCP server over HTTP using the modern StreamableHTTPServerTransport.

npm start sse

• Port: Configurable via PORT environment variable (defaults to 3000).
• Endpoint:
  • ANY /mcp: Handles both SSE (GET) and MCP messages (POST).

Setup

Prerequisites

• Node.js installed.
• Access to an MS SQL Server instance.

Configuration

Set the following environment variables:

• DB_USER: Database username.
• DB_PASSWORD: Database password.
• DB_SERVER: Server hostname/IP (defaults to localhost).
• DB_NAME: Database name.
• PORT: (Optional) Port for SSE mode.

Installation

npm install
npm run build

Running with MCP Inspector

npx @modelcontextprotocol/inspector node dist/index.js

Security

• The query_data tool is strictly limited to SELECT statements.
• Parameters are supported and recommended to prevent SQL injection.
• Multiple statements (;) are blocked.