Microsoft SQL Server — MCP server for Claude Code: schema, queries
Lets your agent read a SQL Server schema, run SELECT-only queries and inspect execution plans. Writes stay off until you turn them on per profile.
Open on GitHubWhat Microsoft SQL Server does
The server starts read-only. An agent can pull metadata, run a parameterized query and look at how the plan executes. Writing is a separate switch, set through AllowWrite on a given profile.
A profile holds one connection: the connection string, row and timeout caps, and whether writes are permitted. default always exists; other profiles come from appsettings.json or variables shaped like McpMssql__Profiles__<NAME>__<FIELD>. One deployment can reach several servers.
You need .NET 8.0 or later and a connection string. Without one the server will not boot — a profile missing ConnectionString, even an unconfigured default, fails at startup. Caps are enforced: Query:MaxRows cannot go past 1000 and Query:CommandTimeoutSeconds past 300, so an oversized value gets clamped and logged to stderr. Treat AllowWrite as a soft guard rather than a database permission; a db_datareader login is what actually blocks writes.
What it helps with
- inspect tables and relationships without opening SSMS
- run a parameterized SELECT safely
- find out why a slow query drags
- reach several MSSQL servers from one agent setup
- allow writes for a migrations profile only
Example prompts for the agent
- List the tables in the dbo schema with their columns
- Run this against the
warehouseprofile: monthly revenue for last year - Explain the execution plan and tell me where it slows down
How to install Microsoft SQL Server
Install
The MCP registry has no launch command for it: see the repository README
Step by step, with commands for each platform: How to add an MCP server to Claude Code, Codex, Cursor, VS Code, Gemini CLI and more
Questions about Microsoft SQL Server
How do I install the Microsoft SQL Server MCP server?
Install it as a global tool with dotnet tool install --global Alyio.McpMssql --prerelease. Then set MCPMSSQL_CONNECTION_STRING and start mcp-mssql.
What does this MCP server do?
It exposes schema discovery, parameterized SELECT queries and execution-plan analysis to your agent. Writes stay disabled until a profile enables them.
Can it connect to more than one SQL Server?
Yes. Define profiles in appsettings.json or via McpMssql__Profiles__<NAME>__<FIELD> variables, and pass the optional profile argument on a tool call.
