RoselineMCP — MCP server for C#: Roslyn code analysis
Gives a coding agent a structural view of a C# solution — symbols, references, call graphs, member-level edits — instead of whole-file reads.
Open on GitHubWhat RoselineMCP does
RoselineMCP exposes the Roslyn compiler platform as an MCP server. The agent asks where a symbol is declared, who calls a method, which types implement an interface, and gets an answer built from the solution's structure. Edits work the same way: a single member is replaced, added or deleted, a rename spans the whole solution, and the result comes back as a unified diff rather than a rewritten file. Preview is the default.
The seven navigation tools plus the diagnostics and patch tools never touch disk. Writing requires an explicit previewOnly: false. Diagnostics come from Roslyn and Roslynator analyzers, and each one can arrive with an automated fix as a reviewable patch.
Startup goes through dnx, the .NET counterpart to npx, so there is no install step. The .NET 10 SDK is required. A NuGet global tool and Docker are also available. An optional PostToolUse hook runs the compiler after any file write, not only after RoselineMCP's own edits.
What it helps with
- find every caller of a method across a solution
- rename a symbol in all projects at once
- collect analyzer diagnostics with ready patches
- swap out one class member without rewriting the file
- outline a file's shape without reading it end to end
Example prompts for the agent
- Find every caller of
OrderService.Checkoutin the solution - Rename
FootoBaracross the solution and show me the diff - Run diagnostics on the solution and propose patches
How to install RoselineMCP
Install
The MCP registry has no launch command for it: see the repository README
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 RoselineMCP
How do I install RoselineMCP in Claude Code?
Add the server to your MCP client config: "roseline": { "command": "dnx", "args": ["RoselineMCP", "--yes"] }. No separate install is needed, but the .NET 10 SDK is.
What does RoselineMCP do?
It answers structural questions about C# code through Roslyn: where a symbol lives, where it is used, who calls it, what derives from a type. It also applies member-level edits and gathers diagnostics with fixes.
Does RoselineMCP write to my files on its own?
No. Navigation and diagnostics are read-only, and the three write tools only run when previewOnly: false is passed explicitly.
