Microsoft SQL Server MCP server

MCP SQL Server

<!-- mcp-name: io.github.alyiox/mcp-mssql -->

A read-only-by-default Model Context Protocol (MCP) server for Microsoft SQL Server that provides schema discovery, select-only queries, execution-plan analysis, opt-in writes, and profile-based access to multiple servers from a single toolset deployment.

Requirements: .NET 8.0 or later runtime (the tool targets net8.0 and net10.0), SQL Server, and a connection string.

Quick start

Set MCPMSSQLCONNECTIONSTRING and run the server in one of these ways:

# Option 1: Run from NuGet package (e.g. with MCP Inspector)
export MCPMSSQL_CONNECTION_STRING="Server=127.0.0.1;User ID=sa;Password=<YourStrong@Passw0rd>;Encrypt=True;TrustServerCertificate=True;"
npx -y @modelcontextprotocol/inspector@latest dotnet dnx Alyio.McpMssql --prerelease

# Option 2: Install and run as a global tool
dotnet tool install --global Alyio.McpMssql --prerelease
export MCPMSSQL_CONNECTION_STRING="Server=127.0.0.1;User ID=sa;Password=<YourStrong@Passw0rd>;Encrypt=True;TrustServerCertificate=True;"
npx -y @modelcontextprotocol/inspector@latest mcp-mssql

# Option 3: Run from source (clone repo, then)
export MCPMSSQL_CONNECTION_STRING="Server=127.0.0.1;User ID=sa;Password=<YourStrong@Passw0rd>;Encrypt=True;TrustServerCertificate=True;"
npx -y @modelcontextprotocol/inspector@latest dotnet run --project src/Alyio.McpMssql -f net10.0

Configuration

A profile is one SQL Server connection: a connection string, the row and timeout caps that apply to it, and whether writes are allowed. A profile named default always exists; every tool takes an optional profile to reach another, and list_profiles reports what is configured.

Settings come from three sources, merged field by field, later winning:

1. the user-scoped appsettings.json — any number of profiles;
2. McpMssqlProfiles_ environment variables — any number of profiles;
3. flat MCPMSSQL_ environment variables — the default profile only.

Because the merge is per field rather than per profile, an appsettings.json can carry the full set while a flat MCPMSSQLCONNECTIONSTRING repoints the default profile at a local server, leaving its other fields intact. There is no fallback connection string: a profile without one — including a default that nothing configured — fails startup.

Each setting has one field name, spelled three ways — the JSON path under McpMssql:Profiles:, that same path with : replaced by __ as an environment variable, or the flat form:

Shortened. The full README is on GitHub.