Skip to main content

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": ["/absolute/path/to/YourSolution.sln"]
    }
  }
}

Solution paths are passed as bare arguments — there is no --solution flag. Pass several to load them all at once and switch with set_active_solution:

{
  "mcpServers": {
    "roslyn-codelens": {
      "command": "roslyn-codelens-mcp",
      "args": [
        "/absolute/path/to/First.slnx",
        "/absolute/path/to/Second.slnx"
      ]
    }
  }
}

Arguments are optional. With none, the server searches the working directory for a .sln/.slnx; if it finds nothing it still starts, prints a notice to stderr, and tools return errors until you call load_solution.

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.