mcp-server-mssql

A Model Context Protocol server that gives LLM agents safe, structured access to Microsoft SQL Server: schema inspection plus row-level CRUD, every operation parameterized and logged.

Built because agents working against real business databases need more than "run this SQL string" — they need typed tools with predictable failure modes.

How it works

flowchart LR
    A[MCP client<br/>Claude Desktop / Claude Code] -- stdio --> B[mcp-server-mssql]
    B --> C[connection pool<br/>mssql driver]
    C --> D[(SQL Server)]
    B -. structured logs .-> E[logs/]

The server connects to a single database configured via environment variables and exposes six tools. All queries are parameterized — table and column names are validated against the live schema before any statement runs, so an agent cannot inject through identifiers.

Tools

| Tool | What it does |
|---|---|
| list_tables | List all user tables in the configured database |
| get_table_schema | Column names, types, nullability, and defaults for a table |
| read_table_rows | Read rows with optional column selection, WHERE filters, ORDER BY, and LIMIT |
| create_table_records | Insert one or more rows (column/value validated against schema) |
| update_table_records | Update rows matching a filter; returns affected count |
| delete_table_records | Delete rows matching a filter; returns affected count |

Example interaction

> User: "Which customers signed up this month?"
>
> Agent calls list_tables → finds Customers → calls get_table_schema {"table_name": "Customers"} → sees CreatedAt datetime2 → calls read_table_rows {"table_name": "Customers", "filters": {"CreatedAt": {">=": "2026-07-01"}}, "limit": 50} → answers with the rows.

Setup

Requires Node.js 18+ and network access to a SQL Server instance.

git clone https://github.com/TerraCo89/mcp-server-mssql.git
cd mcp-server-mssql
npm install
cp .env.example .env   # fill in connection details
npm run build

Configuration (environment variables)

| Variable | Required | Notes |
|---|---|---|
| MSSQL_HOST / MSSQL_PORT | yes / no | Port defaults to 1433 |
| MSSQL_USER / MSSQL_PASSWORD | yes | SQL auth credentials |
| MSSQL_DATABASE | yes | Single database per server instance |
| MSSQL_ENCRYPT, MSSQL_TRUST_SERVER_CERTIFICATE | no | TLS options |
| LOG_LEVEL | no | info by default |

Use with Claude Desktop / Claude Code

{
  "mcpServers": {
    "mssql": {
      "command": "node",
      "args": ["/path/to/mcp-server-mssql/dist/server.js"],
      "env": {
        "MSSQL_HOST": "localhost",
        "MSSQL_USER": "agent_reader",
        "MSSQL_PASSWORD": "...",
        "MSSQL_DATABASE": "MyDb"
      }
    }
  }
}

Tip: point it at a least-privilege SQL login — the server can only do what the login can.

Development

npm run dev    # ts-node with live reload
npm test       # jest test suite (src/*.test.ts, tests/)
npm run build  # emit dist/

Docker: docker build -t mcp-server-mssql . then run with the same environment variables.

License

MIT