SharpLens — Claude Code MCP server: what it does, how to install
Deep semantic inspection and refactoring for C# and .NET solutions via Roslyn. Helps agents trace symbol usages, spot missing cancellation tokens, and calculate change impact.
claude mcp add --env DOTNET_SOLUTION_PATH=<DOTNET_SOLUTION_PATH> --env ROSLYN_LOG_LEVEL=<ROSLYN_LOG_LEVEL> --env ROSLYN_TIMEOUT_SECONDS=<ROSLYN_TIMEOUT_SECONDS> --transport stdio sharplens -- npx -y sharplens-mcpWhat SharpLens does
The server gives coding agents direct access to Microsoft Roslyn compiler data. It supplies 92 tools tailored for inspecting and editing .NET codebases. This setup handles type hierarchies, complexity metrics, unused declarations, and asynchronous methods that lack a cancellation token. Plain text searches miss these nuances.
SharpLens stores an in-memory snapshot of the whole workspace. You supply the path to a .sln, .slnx, or .slnf file with DOTNET_SOLUTION_PATH, or call load_solution inside the session. Multi-targeted projects merge their diagnostic output under a unified project entry with a targetFrameworks tag.
External edits made outside the server tools require a follow-up call to sync_documents. Omitting this sync triggers a STALE_DOCUMENT rejection on the next update attempt. Files lacking a UTF-8 BOM that cannot reproduce their original bytes will fail with UNSUPPORTED_ENCODING.
What it helps with
- spot asynchronous methods lacking cancellation tokens
- evaluate breaking changes across dependent code
- detect dead code and calculate complexity scores
- rename symbols safely across .NET solutions
Example prompts for the agent
- Find all asynchronous methods in the solution missing a CancellationToken.
- Check the impact of modifying the OrderProcessor class across the project.
- Run sync_documents for the changed files in src.
How to install SharpLens
Platform CLI
claude mcp add --env DOTNET_SOLUTION_PATH=<DOTNET_SOLUTION_PATH> --env ROSLYN_LOG_LEVEL=<ROSLYN_LOG_LEVEL> --env ROSLYN_TIMEOUT_SECONDS=<ROSLYN_TIMEOUT_SECONDS> --transport stdio sharplens -- npx -y sharplens-mcpReplace <…> with your own values
Platform CLI
codex mcp add sharplens --env DOTNET_SOLUTION_PATH=<DOTNET_SOLUTION_PATH> --env ROSLYN_LOG_LEVEL=<ROSLYN_LOG_LEVEL> --env ROSLYN_TIMEOUT_SECONDS=<ROSLYN_TIMEOUT_SECONDS> -- npx -y sharplens-mcpReplace <…> with your own values
Config file
{
"mcpServers": {
"sharplens": {
"command": "npx",
"args": [
"-y",
"sharplens-mcp"
],
"env": {
"DOTNET_SOLUTION_PATH": "<DOTNET_SOLUTION_PATH>",
"ROSLYN_LOG_LEVEL": "<ROSLYN_LOG_LEVEL>",
"ROSLYN_TIMEOUT_SECONDS": "<ROSLYN_TIMEOUT_SECONDS>"
}
}
}
}Replace <…> with your own values
Config file
{
"servers": {
"sharplens": {
"type": "stdio",
"command": "npx",
"args": [
"-y",
"sharplens-mcp"
],
"env": {
"DOTNET_SOLUTION_PATH": "<DOTNET_SOLUTION_PATH>",
"ROSLYN_LOG_LEVEL": "<ROSLYN_LOG_LEVEL>",
"ROSLYN_TIMEOUT_SECONDS": "<ROSLYN_TIMEOUT_SECONDS>"
}
}
}
}Replace <…> with your own values
Platform CLI
gemini mcp add -e DOTNET_SOLUTION_PATH=<DOTNET_SOLUTION_PATH> -e ROSLYN_LOG_LEVEL=<ROSLYN_LOG_LEVEL> -e ROSLYN_TIMEOUT_SECONDS=<ROSLYN_TIMEOUT_SECONDS> sharplens npx -y sharplens-mcpReplace <…> with your own values
Step by step, with commands for each platform: How to add an MCP server to Claude Code, Codex, Cursor, VS Code, Gemini CLI and more
Questions about SharpLens
How to install SharpLens in Claude Code?
Run claude mcp add sharplens -- npx -y sharplens-mcp. To specify solution paths and parameters upfront, run `claude mcp add --env DOTNET_SOLUTION_PATH=<DOTNET_SOLUTION_PATH> --env ROSLYN_LOG_LEVEL=<ROSLYN_LOG_LEVEL> --env ROSLYN_TIMEOUT_SECONDS=<ROSLYN_TIMEOUT_SECONDS> --transport stdio sharplens -- npx -y sharplens-mcp`.
What does SharpLens do?
It connects AI coding agents to the Roslyn compiler engine for semantic C# and .NET inspection. The server exposes tools for symbol lookup, dead code detection, complexity calculation, and safe refactoring.
Why does SharpLens return a STALE_DOCUMENT error?
The server tracks solution state in memory. If an agent edits .cs files using external editor commands, it must invoke sync_documents before running further updates, or the server will refuse to write stale files.
