Roslyn Codelens MCP

What MarcelRoozekrans/roslyn-codelens-mcp MCP server does

MarcelRoozekrans/roslyn-codelens-mcp MCP server gives MCP-compatible AI agents access to semantic information from .NET projects. It uses Roslyn to understand symbols and relationships instead of treating source files as plain text. The tool set includes code navigation, dependency analysis, diagnostics, test coverage discovery, quality checks, API comparison, and refactoring operations.

The server can locate implementations, callers, references, definitions, event subscriptions, attribute usages, and tests for a symbol. It can also explain type hierarchies, project dependencies, dependency-injection registrations, construction options, exception flow, reflection usage, and NuGet references. For API and maintenance work, it can enumerate public surfaces, compare them with a JSON or DLL baseline, find obsolete usage, detect circular dependencies, and inspect source-generator output.

How it works

Roslyn provides the semantic model used to resolve types, members, inheritance, calls, diagnostics, and source locations. The project description states that the server builds indexes for fast lookups. Results can include precise occurrence kinds and source columns, which allows callers to distinguish reads, writes, invocations, object creation, casts, declarations, and other reference forms.

Several capabilities operate across project boundaries. For example, dependency-injection analysis recognizes generic registrations, typeof pairs, and factory-lambda forms. Instantiation analysis combines constructors, static factories, registrations, and required members, and can account for InternalsVisibleTo when evaluating whether a particular project can access an option. Test-oriented tools can walk through helpers transitively, generate a compilable test-class skeleton, and identify public members that no test reaches.

The server also supports source inspection and changes. It can return complete member declarations, inspect external assemblies and IL, provide compiler or analyzer diagnostics, return structured code fixes, discover code actions, and apply a selected Roslyn action with a preview diff before writing changes.

Setup and configuration

The repository publishes a NuGet package named RoslynCodeLens.Mcp and an npm package named roslyn-codelens-mcp. The supplied material also identifies a hosted deployment on Fronteir AI. No required environment variables, API keys, or configuration values are described in the provided documentation.

For local MCP client setup, use the package distribution appropriate to the client and runtime environment. The exact README excerpt does not provide a full client configuration block, so settings such as workspace selection, project loading, or solution paths should be verified in the repository documentation before deployment.

Tools and capabilities

The documented capabilities include:

• Navigate symbols, implementations, callers, definitions, references, hierarchies, and event subscriptions.
• Inspect diagnostics, code fixes, refactorings, generated code, external assemblies, and IL.
• Analyze tests, uncovered symbols, test summaries, constructor dependencies, and test skeletons.
• Review architecture boundaries, project cycles, API breaking changes, obsolete calls, and NuGet dependencies.
• Measure complexity, detect large classes, god objects, unused symbols, naming and async violations, and disposable misuse.
• Check source generators, reflection, exception propagation, catches, throws, DI registrations, and project health.

MarcelRoozekrans/roslyn-codelens-mcp MCP server is therefore best suited to repository-aware .NET maintenance, review, navigation, and refactoring workflows.