AlterRoslynMcp

An MCP server that provides AI agents with Roslyn-based code analysis capabilities

Get It on NuGet

This project uses Roslynator, licensed under Apache 2.0.

Installation

dotnet tool install -g AlterRoslynMcp

Update

dotnet tool update -g AlterRoslynMcp

MCP config (OpenCode)

  "mcp": {
    "roslyn": {
      "type": "local",
      "command": [
        "AlterRoslynMcp"
      ]
    }
  }

What It Is

RoslynMcp is a .NET application that exposes the power of Roslyn (the .NET compiler platform) through the MCP protocol. It acts as a bridge between AI assistants and your C# codebase, enabling deep code understanding and analysis.

Why It Exists

Traditional AI code assistants often rely on simplistic pattern matching (grep/glob) which misses semantic context. RoslynMcp solves this by providing:

• Semantic understanding — It knows what your code means, not just what it says
• Symbol resolution — Understands types, methods, properties across your entire solution
• Call graph tracing — See how code flows through your system
• Code smell detection — Identifies potential issues using Roslynator analyzers

What You Can Use It For

Inspection Tool	Description
Load Solution	Loads a .sln/.slnx file and prepare the workspace
Understand Projects	Explore project relationships, types, and deep-profile hotspots
List Types	Discover all classes, interfaces, enums in a project
List Members	Explore methods, properties, fields of any type
Resolve Symbol	Get canonical IDs for a single code symbol
Resolve Symbols	Resolve multiple symbols in one round-trip
Explain Symbol	Understand what a symbol does and where it's used
Trace Call Flow	See upstream callers or downstream callees
Find Callers	Return only immediate direct upstream callers
Find Callees	Return only immediate direct downstream callees
Find Usages	Locate all references to a type/member
Find Implementations	Locate all implementations of a interface or abstract class/method
Get Type Hierarchy	Explore type inheritance and derived types
Find Code Smells	Detect potential issues in a file
Run Tests	Run .NET tests for the loaded solution or a specific target

Mutation Tool	Description
Add Method	Add a helper or overload to an existing type using symbol-aware insertion
Replace Method	Replace a full method declaration when name, signature, or modifiers must move
Replace Method Body	Change only method logic while preserving the existing declaration shape
Delete Method	Remove an obsolete method or disposable helper by exact symbol target
Rename Symbol	Rename operation for types, methods, etc.
Format Document	Format a C# source file using the solution's settings

A detailed description of all tools is available in the Wiki.