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Installation

Prerequisites​

  • .NET 10 SDK or later
  • A .NET solution (.sln or .slnx file)

Install the tool​

dotnet tool install -g RoslynCodeLens.Mcp

Verify the install:

roslyn-codelens-mcp --version

Configure .mcp.json​

Add the server to your project's .mcp.json (or ~/.claude/.mcp.json for global config):

{
  "mcpServers": {
    "roslyn-codelens": {
      "command": "roslyn-codelens-mcp",
      "args": ["--solution", "/absolute/path/to/YourSolution.sln"]
    }
  }
}

The --solution argument is required on first start. Alternatively, use the ROSLYN_CODELENS_SOLUTION environment variable:

{
  "mcpServers": {
    "roslyn-codelens": {
      "command": "roslyn-codelens-mcp",
      "env": {
        "ROSLYN_CODELENS_SOLUTION": "/absolute/path/to/YourSolution.sln"
      }
    }
  }
}

Verify the server starts​

Restart your MCP client (Claude Code, etc.). The server loads the solution on startup — this takes 5–30 seconds for large solutions.

Once loaded, try:

Use get_type_overview to describe the type MyClass

If the server responds with type info, setup is complete.