C# Class Analyzer MCP

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CSharpAnalyserMcp

A read-only Model Context Protocol (MCP) server that lets an AI assistant browse any C# solution through Roslyn.

The server loads a solution with MSBuildWorkspace into a cached Roslyn snapshot and then answers structured queries about it: where each type is declared, its XML documentation, and a method's signature, documentation, source location and body. An agent can therefore pull in the exact slice of source it needs instead of reading whole files into its context window.

• Transport: stdio (StdioServerTransport), protocol traffic on stdout only; all logs go to stderr.
• Solution path is passed on the command line (--workspace ); the solution is loaded before the MCP handshake, so a bad path fails fast with a message on stderr and a non-zero exit code.
• Every tool returns MCP text content and never structuredContent: listing / hierarchy / search tools return one text block per entry (a string list from the client's point of view), while detail tools emit path / desc / namespace / signature / body blocks separated by a line containing ---.
• Distribution: published to NuGet as the .NET tool CSharpAnalyserMcp (command csharp-analyser-mcp) and listed in the official MCP Registry as io.github.undy-mosq/CSharpAnalyserMcp.

Installation

NuGet .NET tool (recommended)

dotnet tool install --global CSharpAnalyserMcp

csharp-analyser-mcp --workspace D:\MyProject\MySolution.sln

upgrade / remove

dotnet tool update --global CSharpAnalyserMcp dotnet tool uninstall --global CSharpAnalyserMcp

Install it globally: a --local install only writes a manifest entry, so csharp-analyser-mcp never lands on PATH and MCP clients cannot start it.

On demand with dnx (nothing to install, .NET SDK 10+)

# "--" separates dnx options from the arguments forwarded to the server

dnx CSharpAnalyserMcp --yes -- --workspace D:\MyProject\MySolution.sln

From source

git clone https://github.com/undy-mosq/CSharpAnalyserMcp

dotnet build CSharpAnalyserMcp\CSharpAnalyserMcp.csproj dotnet run --project CSharpAnalyserMcp -- --workspace D:\MyProject\MySolution.sln

Requirements

Client configuration

The server is started with a single argument, --workspace, pointing at the solution file.

Installed .NET tool

The global tool shim lives in %USERPROFILE%\.dotnet\tools. MCP clients spawn the process themselves and only see the PATH they inherited, so point the configuration at the shim by absolute path (expand %USERPROFILE%, e.g. C:\Users\you\.dotnet\tools\csharp-analyser-mcp.exe):

Claude Desktop (claude_desktop_config.json):

{

"mcpServers": { "csharp-analyser": { "command": "C:\\Users\\you\\.dotnet\\tools\\csharp-analyser-mcp.exe", "args": ["--workspace", "D:\\MyProject\\MySolution.sln"] } } }

VS Code (.vscode/mcp.json):

{

"servers": { "csharp-analyser": { "type": "stdio", "command": "C:\\Users\\you\\.dotnet\\tools\\csharp-analyser-mcp.exe", "args": ["--workspace", "D:\\MyProject\\MySolution.sln"] } } }

The bare command name ("command": "csharp-analyser-mcp") works only when that directory is already on the client's PATH; a client started before the tool was installed keeps the old environment, so restart it after changing PATH.

On demand with dnx (nothing installed)

{

"servers": { "csharp-analyser": { "type": "stdio", "command": "dnx", "args": ["CSharpAnalyserMcp", "--yes", "--", "--workspace", "D:\\MyProject\\MySolution.sln"] } } }

Append @ to the package id to pin a version. The MCP Server tab of the NuGet package page offers the same JSON for copying. dnx is a .cmd shim; if the client cannot spawn it, use the equivalent dotnet form instead: "command": "dotnet" with "args": ["tool", "exec", "CSharpAnalyserMcp", "--yes", "--", "--workspace", "D:\\MyProject\\MySolution.sln"].

Published executable

VS Code (.vscode/mcp.json):

{

"servers": { "csharp-analyser": { "type": "stdio", "command": "C:\\Tools\\csharp-analyser\\CSharpAnalyserMcp.exe", "args": ["--workspace", "D:\\MyProject\\MySolution.sln"] } } }

Running the project from source

{

"servers": { "csharp-analyser": { "type": "stdio", "command": "dotnet", "args": [ "run", "--project", "D:\\MyProject\\CSharpAnalyserMcp\\CSharpAnalyserMcp\\CSharpAnalyserMcp.csproj", "--", "--workspace", "D:\\MyProject\\MySolution.sln" ] } } }

Press F5 in VS Code to debug the server itself; .vscode/launch.json already passes a --workspace argument — point it at your own solution.

Tools

list_classes_in_folder

{ "folderPath": "src/Services", "kinds": ["class", "interface"] }

Files under bin/obj are skipped. Returns a string list, one text content per type, formatted as {relativePath} L{start}-{end} {namespace}: {signature}; the namespace segment is omitted for the global namespace, and a partial type reports the location of its first declaration plus a trailing ...(partial xN).

list_classes_in_namespace

{ "namespaceName": "MyApp.Services", "includeSubNamespaces": true, "kinds": ["all"] }

get_class_documentation

{ "typeDeclaration": "public static class ItemConfig", "maxXmlChars": 2000 }

On a match the result is a text block: path / desc / namespace (the global namespace prints as global) / signature / body (member signatures, one per line); multiple matches are separated by a line containing ---. A miss prints (no match) followed by candidates : and candidate declaration lines.

get_method

{ "methodDeclaration": "public static void SetEffect(RoleAttributes owner, int stack)", "typeDeclaration": "public class RoleAttributes", "namespaceName": "DuelModel" }

Matching rules:

• Both declaration lines must match the canonical signature or the first source line of the declaration exactly after whitespace is stripped (no substring matching).
• Only members declared by the type itself are searched (ordinary methods; no inherited members, constructors or properties). Explicit interface implementations (IFoo.Bar) are matched too.
• Parameter types parsed from the declaration line are compared case-insensitively and whitespace-insensitively, without namespace prefixes; C# aliases are mapped to their metadata names (int → Int32, string → String, …). The comparison is relaxed step by step: exact → ignoring generic arguments → allowing a prefix of the parameter list.
• When nothing matches, (no match) is printed followed by candidates : and candidate declaration lines (same-named methods of that type first, otherwise every method of that type).

The result is a text block per overload: path / desc (raw XML docs, 2000-char cap) / namespace / class / signature / body (source with the outermost braces and the common indentation removed); overloads are separated by a line containing ---.

find_inheritance

{ "typeDeclaration": "public abstract class BuffEntity", "namespaceName": "Duel" }

The first entry is the queried type itself (no indentation, no prefix); every derived type follows as its own text content, indented by one tab and prefixed with - per hierarchy level. A class root reports the classes / records deriving from it; an interface root reports sub-interfaces plus the classes / structs / records implementing it directly. Generic base types are matched by OriginalDefinition (Base and Base count as the same base). Ea