roslyn-mcp

Roslyn MCP Server

Let AI assistants like Claude safely refactor your C# codebase using the same Roslyn compiler platform that powers Visual Studio.

Roslyn MCP Server is a Model Context Protocol (MCP) server that exposes 41 Roslyn-powered tools to AI assistants and other MCP clients. It combines 19 refactoring operations, 5 code navigation tools, 6 analysis and metrics tools, 4 code generation tools, and 7 code conversion tools -- giving your AI deep code intelligence, comprehensive refactoring, and modern C# syntax transformations with full solution-wide reference tracking and preview support.

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Table of Contents

• Why RoslynMcpServer?
• Prerequisites
• Quick Start
• Standalone CLI
• Configuration
• Available Tools
• Preview Mode
• Troubleshooting
• NuGet Libraries
• Contributing
• License

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Why RoslynMcpServer?

• 41 tools -- refactoring, navigation, analysis, generation, and conversion tools, the most comprehensive Roslyn MCP server available
• Preview mode on every operation -- see exactly what will change before applying
• Atomic file writes with rollback -- if any file write fails, all changes are reverted
• Solution-wide reference updates -- renames and moves propagate across your entire solution
• Single command install -- dotnet tool install -g RoslynMcp.Server, no repo cloning needed
• Cross-platform -- works on Windows, Linux, and macOS

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Prerequisites

Before installing, make sure you have:

1. .NET 9.0 SDK or later -- Download here
2. A C# solution (.sln or .slnx) or project (.csproj) to work with

Verify your .NET SDK version:

dotnet --version

The output should be 9.0.x or higher.

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Quick Start

1. Install

dotnet tool install -g RoslynMcp.Server

2. Configure

Create a .mcp.json file in your project root (for Claude Code):

{
  "mcpServers": {
    "roslyn-refactor": {
      "type": "stdio",
      "command": "roslyn-mcp",
      "args": []
    }
  }
}

Then restart Claude Code or run /mcp to connect.

3. Verify

Ask Claude:

"Run the roslyn diagnose tool for my solution at C:/path/to/MySolution.sln"

You should see a health report with Roslyn version, MSBuild status, and workspace details.

4. Try It

Ask Claude:

"Rename the class UserService to AccountService in C:/path/to/MySolution.sln"

Claude will use the rename_symbol tool to rename the class and update every reference across your entire solution.

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Standalone CLI

All 41 tools are also available as a standalone CLI for use in scripts, CI/CD pipelines, and terminals without an AI assistant.

Install

dotnet tool install -g RoslynMcp.Cli

Usage

roslyn-cli <solution-path> <tool-name> [--option value ...]
roslyn-cli <tool-name> --help
roslyn-cli --help

Examples

# Check environment health
roslyn-cli C:/path/to/MySolution.sln diagnose --format text

# Rename a symbol across the entire solution
roslyn-cli C:/path/to/MySolution.sln rename-symbol --source-file C:/path/to/Foo.cs --symbol-name Bar --new-name Baz

# Get compiler diagnostics (errors only), pipe to jq
roslyn-cli C:/path/to/MySolution.sln get-diagnostics --severity-filter Error | jq '.data'

# Preview a refactoring without applying
roslyn-cli C:/path/to/MySolution.sln extract-method --source-file Foo.cs --start-line 10 --end-line 20 --method-name DoWork --preview

Output is JSON by default (pipeable to jq). Use --format text for human-readable output. Exit codes: 0=success, 1=tool error, 2=CLI error, 3=environment error.

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Configuration

Claude Code

Create .mcp.json in your project root:

{
  "mcpServers": {
    "roslyn-refactor": {
      "type": "stdio",
      "command": "roslyn-mcp",
      "args": []
    }
  }
}

Claude Desktop

Add to your claude_desktop_config.json: