SharpLensMcp

A Model Context Protocol (MCP) server providing 58 AI-optimized tools for .NET/C# semantic code analysis, navigation, refactoring, and code generation using Microsoft Roslyn.

Built for AI coding agents - provides compiler-accurate code understanding that AI cannot infer from reading source files alone.

Installation

Via NuGet (Recommended)

dotnet tool install -g SharpLensMcp

Then run with:

sharplens

Via npm

npx -y sharplens-mcp

Build from Source

dotnet build -c Release
dotnet publish -c Release -o ./publish

Claude Code Setup

1. Install the tool (pick one):

dotnet tool install -g SharpLensMcp
# or
npx -y sharplens-mcp

1. Create .mcp.json in your project root:

{
  "mcpServers": {
    "sharplens": {
      "type": "stdio",
      "command": "npx",
      "args": ["-y", "sharplens-mcp"],
      "env": {
        "DOTNET_SOLUTION_PATH": "/path/to/your/Solution.sln (or .slnx)"
      }
    }
  }
}

1. Restart Claude Code to load the MCP server

2. Verify by asking Claude to run a health check on the Roslyn server

Why Use This with Claude Code?

Claude Code has native LSP support for basic navigation (go-to-definition, find references). SharpLensMcp adds deep semantic analysis:

Configuration

If DOTNET_SOLUTION_PATH is not set, you must call the load_solution tool before using other tools.

AI Agent Configuration Tips

AI models may have trained bias toward using their native tools (Grep, Read, LSP) instead of MCP server tools, even when SharpLensMcp provides better capabilities.

To ensure optimal tool usage:

1. Claude Code: Add to your project's CLAUDE.md:

   For C# code analysis, prefer SharpLensMcp tools over native tools:
   - Use `roslyn:search_symbols` instead of Grep for finding symbols
   - Use `roslyn:get_method_source` instead of Read for viewing methods
   - Use `roslyn:find_references` for semantic (not text) references
   

2. Other MCP clients: Configure tool priority in your agent's system prompt

The semantic analysis from Roslyn is more accurate than text-based search, especially for overloaded methods, partial classes, and inheritance hierarchies.

Agent Responsibility: Document Synchronization

Important: SharpLensMcp maintains an in-memory representation of your solution for fast queries. When files are modified externally (via Edit/Write tools), the agent is responsible for synchronizing changes.

When to call sync_documents:

Usage:

# After editing specific files
sync_documents(filePaths: ["src/MyClass.cs", "src/MyService.cs"])

# After bulk changes - sync all documents
sync_documents()

Why this design?

This mirrors how LSP (Language Server Protocol) works - the client (editor) notifies the server of changes. This approach:

• Eliminates race conditions (agent controls timing)
• Avoids file watcher complexity and platform quirks
• Is faster than full solution reload
• Gives agents explicit control over workspace state

If you don't sync: Queries may return stale data (old method signatures, missing new files, etc.)

Features

• 58 Semantic Analysis Tools - Navigation, refactoring, code generation, diagnostics
• AI-Optimized Descriptions - Clear USAGE/OUTPUT/WORKFLOW patterns
• Structured Responses - Consistent success/error/data format with suggestedNextTools
• Zero-Based Coordinates - Clear warnings to prevent off-by-one errors
• Preview Mode - Safe refactoring with preview before apply
• Batch Operations - Multiple lookups in one call to reduce context usage

Tool Categories

Navigation & Discovery (13 tools)

Analysis (9 tools)

Refactoring (13 tools)

Code Generation (2 tools)

Compound Tools (6 tools)

Infrastructure (5 tools)

Other MCP Clients

For MCP clients other than Claude Code, add to your configuration:

{
  "mcpServers": {
    "sharplens": {
      "command": "sharplens",
      "args": [],
      "env": {
        "DOTNET_SOLUTION_PATH": "/path/to/your/Solution.sln (or .slnx)"
      }
    }
  }
}

Usage

1. Load a solution: Call roslyn:load_solution with path to .sln or .slnx file (or set DOTNET_SOLUTION_PATH)
2. Analyze code: Use any of the 57 tools for navigation, analysis, refactoring
3. Refactor safely: Preview changes before applying with preview: true

Architecture

MCP Client (AI Agent)
        | stdin/stdout (JSON-RPC 2.0)
        v
   SharpLensMcp
   - Protocol handling
   - 57 AI-optimized tools
        |
        v
Microsoft.CodeAnalysis (Roslyn)
  - MSBuildWorkspace
  - SemanticModel
  - SymbolFinder

Requirements

• .NET 8.0 SDK or later — works with .NET 8, 9, 10, and future versions. Analyzes any .NET 8+ project/solution.
• MCP-compatible AI agent

Development

Adding New Tools

1. Add method to src/RoslynService.cs:

public async Task<object> YourToolAsync(string param1, int? param2 = null)
{
    EnsureSolutionLoaded();
    // Your logic...
    return CreateSuccessResponse(
        data: new { /* results */ },
        suggestedNextTools: new[] { "next_tool_hint" }
    );
}

1. Add tool definition to src/McpServer.cs in HandleListToolsAsync

2. Add routing to src/McpServer.cs in HandleToolCallAsync switch

3. Build and publish:

dotnet build -c Release
dotnet publish -c Release -o ./publish

Key Files

License

MIT - See LICENSE for details.