MS SQL Server MCP Server

MS SQL Server MCP Server v3.0.0

🚀 Model Context Protocol (MCP) server for Microsoft SQL Server - compatible with Claude Desktop, Cursor, Windsurf and VS Code.

Standards Alignment

• Protocol target: MCP draft/latest spec
• Transport spec: Transports
• Security: Security best practices
• SDK: @modelcontextprotocol/server / @modelcontextprotocol/client / @modelcontextprotocol/node v2 (2.0.0), targeting the 2026-07-28 MCP spec
• Requires Node.js >= 20

🚀 Quick Start

1. Install

npm install -g mssql-mcp

2. Configure IDE

Claude Desktop (claude_desktop_config.json):

{
  "mcpServers": {
    "mssql": {
      "command": "npx",
      "args": ["-y", "mssql-mcp@latest"],
      "env": {
        "DB_SERVER": "your-server.com",
        "DB_DATABASE": "your-database",
        "DB_USER": "your-username",
        "DB_PASSWORD": "your-password",
        "DB_ENCRYPT": "true",
        "DB_TRUST_SERVER_CERTIFICATE": "true"
      }
    }
  }
}

Cursor/Windsurf/VS Code (.vscode/mcp.json):

{
  "servers": {
    "mssql": {
      "command": "npx",
      "args": ["-y", "mssql-mcp@latest"],
      "env": {
        "DB_SERVER": "your-server.com",
        "DB_DATABASE": "your-database",
        "DB_USER": "your-username",
        "DB_PASSWORD": "your-password",
        "DB_ENCRYPT": "true",
        "DB_TRUST_SERVER_CERTIFICATE": "true"
      }
    }
  }
}

HTTP transport (remote/hosted scenarios):

{
  "servers": {
    "mssql": {
      "type": "http",
      "url": "http://127.0.0.1:3001",
      "env": {}
    }
  }
}

Replace with your actual database credentials. Credentials are read from the server environment only — never passed as tool parameters.

��️ Tool Catalog

Primary tools (use these)

Tool	Read-only	Description
mssql_connect_database	No	Connect using env variables. Idempotent.
mssql_disconnect_database	No	Close connection. Idempotent.
mssql_connection_status	✅	Connection state and pool metrics
mssql_run_sql_query	⚠️ No	Execute arbitrary SQL. May mutate data.
mssql_list_schema_objects	✅	List tables/views/procedures/functions with pagination
mssql_describe_table_columns	✅	Column definitions for a table
mssql_read_table_rows	✅	Paginated rows with projection and safe WHERE
mssql_execute_stored_procedure	⚠️ No	Execute a stored procedure
mssql_list_databases	✅	List all databases on the instance

All data tools accept a response_format parameter ("json" | "markdown", default "json"). Use "markdown" to get human-readable table output.

Deprecated aliases (still registered for backward compatibility)

These are the only alias tool names the server actually registers (in src/tools/*.ts). They behave the same as their replacement but are not documented in new integrations — use the primary tool names above instead.

Old name	Use instead
mssql_execute_query	mssql_run_sql_query
mssql_get_schema	mssql_list_schema_objects
mssql_describe_table	mssql_describe_table_columns
mssql_get_table_data	mssql_read_table_rows
mssql_execute_procedure	mssql_execute_stored_procedure

🚌 Transport Modes

Mode	Use when
stdio (default)	Local IDE integration (Claude Desktop, Cursor, VS Code)
http	Remote/hosted deployment, testing with MCP Inspector

# stdio (default)
node dist/src/index.js

# HTTP on 127.0.0.1:3001
MCP_TRANSPORT=http node dist/src/index.js

# Custom HTTP host/port
MCP_TRANSPORT=http MCP_HOST=0.0.0.0 MCP_PORT=8080 node dist/src/index.js

🔧 Environment Variables

Database connection

Variable	Required	Default	Description
DB_SERVER	✅	—	SQL Server hostname or IP
DB_DATABASE	❌	—	Database name
DB_USER	❌	—	Login username
DB_PASSWORD	❌	—	Login password
DB_PORT	❌	1433	TCP port
DB_ENCRYPT	❌	true	Enable TLS (required for Azure SQL)
DB_TRUST_SERVER_CERTIFICATE	❌	false	Trust self-signed certs
DB_CONNECTION_TIMEOUT	❌	30000	Connection timeout ms
DB_REQUEST_TIMEOUT	❌	30000	Query timeout ms

Transport

Variable	Default	Description
MCP_TRANSPORT	stdio	stdio or http
MCP_HOST	127.0.0.1	HTTP bind address
MCP_PORT	3001	HTTP port

🔒 Security Model

• No credential parameters: All connection settings come from environment variables only. Tool inputs cannot override connection config.
• Identifier validation: Schema, table, and procedure names are validated against a safe identifier pattern before interpolation into SQL.
• Parameterized queries: All user-supplied values (WHERE clause values, column values) must be passed as named parameters via @paramName — never embedded in query strings.
• Origin and Host validation: HTTP transport validates both the Origin and Host headers against an allowlist (localhost, [::1], and the configured bind host by default), guarding against DNS rebinding.
• SQL risk labeling: run_sql_query and execute_stored_procedure are explicitly labeled as non-read-only and open-world.

⚠️ SQL Risk Notes

run_sql_query accepts arbitrary SQL including DDL and DML. To minimize risk:

• Use a least-privilege SQL login (SELECT-only where possible)
• Never run the server with a sysadmin or sa account
• Consider network firewall rules to limit what the server can reach

📄 Pagination

All list tools return a pagination object:

{
  "count": 20,
  "limit": 20,
  "offset": 0,
  "has_more": true,
  "next_offset": 20,
  "total_count": 150
}

Default page size: 20 rows. Maximum: 200 rows.

Results are also truncated if the serialized payload exceeds 100KB, with a truncation_message explaining how many rows were dropped.

🏗️ Architecture

src/
  index.ts          ← bootstrap (env, transport selection)
  server.ts         ← createServer() factory
  constants.ts      ← limits, defaults, protocol strings
  config.ts         ← env parsing
  types.ts          ← shared TypeScript interfaces
  db/
    connection.ts   ← connection pool singleton
    validators.ts   ← SQL identifier validation
    query-builders.ts ← safe parameterized query construction
  tools/            ← one file per tool group
  resources/        ← MCP resource handlers
  transports/       ← stdio and HTTP transports
  utils/
    errors.ts       ← error normalization helpers
    format.ts       ← JSON formatting, payload truncation
    markdown.ts     ← markdown table/list rendering helpers
    pagination.ts   ← pagination metadata helpers

🧪 Inspector Smoke Test

npx @modelcontextprotocol/inspector

Expected:

• stdio server connects
• Tool list renders with all tools
• mssql_connection_status returns JSON without a connection
• mssql_connect_database works when env variables are set

🔨 Development

npm install
cp .env.example .env  # fill in your test DB credentials
npm run typecheck     # type check only
npm run build         # compile TypeScript
npm test              # run unit tests
npm run ci            # typecheck + build + test

License

MIT © BYMCS