dotnet-roslyn-mcp

Roslyn MCP Server

A Model Context Protocol (MCP) stdio server that exposes Microsoft Roslyn SDK capabilities to AI coding assistants like Claude Code. Provides semantic code analysis, navigation, refactoring, and diagnostics for .NET/C# codebases.

18+ powerful tools including impact analysis, safe refactoring, dead code detection, automated code fixes, batch operations, and dependency visualization!

Features

• Semantic Analysis: 100% compiler-accurate code understanding
• Cross-Solution Navigation: Find references, implementations, callers, and type hierarchies
• Impact Analysis: See what code calls your methods before refactoring
• Safe Refactoring: Rename symbols across solution with preview mode
• Dead Code Detection: Find unused types, methods, and fields
• Real-time Diagnostics: Get compilation errors and warnings
• Symbol Search: Search for types, methods, properties across the solution
• Interface Extraction: Generate interfaces from classes for DI/testability
• Dependency Visualization: Graph project dependencies and detect cycles
• Code Organization: Organize usings, get method overloads, and more

Installation

Prerequisites

• .NET 8.0 SDK or Runtime

Build and Install

# Build the project
dotnet build -c Release

# Pack as global tool
dotnet pack -c Release

# Install globally
dotnet tool install --global --add-source ./src/bin/Release dotnet-roslyn-mcp

# Verify installation
dotnet-roslyn-mcp --version

Configuration

Using Claude Code CLI (Recommended)

After installing the global tool, add it to Claude Code using the CLI:

claude mcp add --transport stdio roslyn \
  --env DOTNET_SOLUTION_PATH="/path/to/your/solution.sln" \
  -- dotnet-roslyn-mcp

Or with additional environment variables:

claude mcp add --transport stdio roslyn \
  --env DOTNET_SOLUTION_PATH="/path/to/your/solution.sln" \
  --env ROSLYN_LOG_LEVEL="Information" \
  --env ROSLYN_MAX_DIAGNOSTICS="100" \
  -- dotnet-roslyn-mcp

Windows:

claude mcp add --transport stdio roslyn ^
  --env DOTNET_SOLUTION_PATH="C:\path\to\your\solution.sln" ^
  --env ROSLYN_LOG_LEVEL="Information" ^
  --env ROSLYN_MAX_DIAGNOSTICS="100" ^
  -- dotnet-roslyn-mcp

Running from Source (Development)

If you want to run the MCP server directly from source without installing it globally:

Linux/macOS:

claude mcp add --transport stdio roslyn \
  --env DOTNET_SOLUTION_PATH="/path/to/your/solution.sln" \
  -- dotnet run --project /path/to/vs-ide-mcp/src/RoslynMcp.csproj

Windows:

claude mcp add --transport stdio roslyn ^
  --env DOTNET_SOLUTION_PATH="C:\path\to\your\solution.sln" ^
  -- cmd /c dotnet run --project C:\path\to\vs-ide-mcp\src\RoslynMcp.csproj

Manual Configuration

Alternatively, create a .claude/mcp-spec.json file in your solution root:

{
  "mcpServers": {
    "roslyn": {
      "command": "dotnet-roslyn-mcp",
      "env": {
        "DOTNET_SOLUTION_PATH": "${workspaceFolder}/YourSolution.sln"
      }
    }
  }
}

Environment Variables

Variable	Default	Description
DOTNET_SOLUTION_PATH	(Required)	Path to .sln file or directory containing it
ROSLYN_LOG_LEVEL	Information	Logging level (Debug, Information, Warning, Error)
ROSLYN_ENABLE_SEMANTIC_CACHE	true	Enable document caching
ROSLYN_MAX_DIAGNOSTICS	100	Maximum diagnostics to return
ROSLYN_INCLUDE_HIDDEN_DIAGNOSTICS	false	Include hidden severity diagnostics
ROSLYN_PARALLEL_ANALYSIS	true	Enable parallel project analysis
ROSLYN_TIMEOUT_SECONDS	30	Operation timeout (increase for large solutions)

Available Tools (18 Total)

Core & Health

1. roslyn:health_check - Check server health and workspace status
2. roslyn:load_solution - Load a .NET solution for analysis
3. roslyn:get_symbol_info - Get detailed semantic information about a symbol

Navigation

1. roslyn:find_references - Find all references to a symbol
2. roslyn:find_implementations - Find all implementations of an interface/abstract class
3. *roslyn:find_callers - Find all methods that call a specific method (impact analysis)

Analysis & Discovery

1. roslyn:get_type_hierarchy - Get inheritance hierarchy for a type
2. roslyn:search_symbols - Search for symbols by name across solution
3. roslyn:get_diagnostics - Get compiler errors and warnings
4. roslyn:find_unused_code - Find dead code (unused types, methods, fields)
5. roslyn:dependency_graph - Visualize project dependencies and detect cycles

Refactoring

1. roslyn:rename_symbol - Safely rename symbol across solution with preview
2. roslyn:extract_interface - Generate interface from class for DI/testability
3. roslyn:organize_usings - Sort and remove unused using directives

Code Fixes & Structure

1. roslyn:get_code_fixes - Get available code fixes for diagnostics
2. roslyn:get_project_structure - Get solution/project structure
3. roslyn:get_method_overloads - Get all overloads of a method
4. roslyn:get_containing_member - Get containing method/property/class info

Example Prompts

Here are some example prompts you can use with Claude Code once the MCP server is configured:

Impact Analysis:

"Find all callers of the ProcessPayment method"
"What code will break if I change this method signature?"
"Who uses the CustomerRepository?"

Safe Refactoring:

"Preview renaming ICustomerRepository to IUserRepository"
"Safely rename ProcessPayment to HandlePayment across the solution"

Dead Code Detection :

"Find all unused code in the Application project"
"What private methods are never called?"
"Show me unused classes in the Domain layer"

Interface Extraction:

"Extract an interface from PaymentService class"
"Generate IPaymentService interface with ProcessPayment and RefundPayment methods"

Dependency Visualization:

"Show me the project dependency graph"
"Are there any circular dependencies?"
"Generate a Mermaid diagram of project dependencies"

Find References:

"Find all references to the ProcessPayment method"
"Where is CustomerService being used?"

Explore Type Hierarchies:

"What classes implement ICustomerRepository?"
"Show me the type hierarchy for CustomerService"
"What interfaces does PaymentProcessor implement?"

Code Navigation:

"Show me all the overloads of ProcessOrder"
"What's the containing class for this method?"
"Search for all methods containing 'Customer'"

Diagnostics:

"Get all compilation errors in the solution"
"Show me warnings in CustomerService.cs"
"What errors are in the Payment project?"

Architecture

┌─────────────────────────────────────┐
│     Claude Code (MCP Client)        │
└───────────────┬─────────────────────┘
                │ stdin/stdout (JSON-RPC 2.0)
┌───────────────▼─────────────────────┐
│          McpServer.cs                │
│  - Protocol handling                 │
│  - Tool registration                 │
│  - Request routing                   │
└───────────────┬─────────────────────┘
                │
┌───────────────▼─────────────────────┐
│       RoslynService.cs               │
│  - Solution management               │
│  - Semantic analysis                 │
│  - Symbol resolution                 │
└───────────────┬─────────────────────┘
                │
┌───────────────▼─────────────────────┐
│  Microsoft.CodeAnalysis (Roslyn)    │
│  - MSBuildWorkspace                  │
│  - SemanticModel                     │
│  - SymbolFinder                      │
└─────────────────────────────────────┘

License

MIT License - Copyright (c) 2025 Brendan Kowitz

See LICENSE file for details.