roslyn-codelens-mcp

# Roslyn CodeLens MCP Server

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A Roslyn-based MCP server that gives AI agents deep semantic understanding of .NET codebases — type hierarchies, call graphs, DI registrations, diagnostics, refactoring, and more.

<a href="https://glama.ai/mcp/servers/MarcelRoozekrans/roslyn-codelens-mcp">
  <img width="380" height="200" src="https://glama.ai/mcp/servers/MarcelRoozekrans/roslyn-codelens-mcp/badge" alt="roslyn-codelens-mcp MCP server" />
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<!-- mcp-name: io.github.MarcelRoozekrans/roslyn-codelens -->

---

## Hosted deployment

A hosted deployment is available on [Fronteir AI](https://fronteir.ai/mcp/marcelroozekrans-roslyn-codelens-mcp).

## Features

- **find_implementations** — Find all classes/structs implementing an interface or extending a class
- **find_callers** — Find every call site for a method, property, or constructor
- **find_event_subscribers** — Every += / -= site for an event symbol, with resolved handler and subscribe/unsubscribe tag
- **find_tests_for_symbol** — List xUnit/NUnit/MSTest methods that exercise a production symbol; opt-in transitive walk through helpers
- **get_test_summary** — Per-project inventory of test methods with framework, attribute kind, data-row count, location, and production symbols referenced
- **find_uncovered_symbols** — Public methods and properties no test transitively reaches; sorted by cyclomatic complexity for prioritization
- **generate_test_skeleton** — Emit a compilable test-class skeleton (as text) for a method or type. Auto-detects xUnit/NUnit/MSTest; surfaces constructor dependencies as TodoNotes; returns a suggested file path. Closes the loop with `find_uncovered_symbols`
- **get_type_hierarchy** — Walk base classes, interfaces, and derived types
- **get_di_registrations** — Scan for DI service registrations
- **get_project_dependencies** — Get the project reference graph
- **get_symbol_context** — One-shot context dump for any type
- **get_public_api_surface** — Enumerate every public/protected type and member in production projects; flat, deterministically-sorted list suitable for API review or breaking-change baselines.
- **find_breaking_changes** — Diff the current API against a baseline JSON or DLL; report removed members, kind changes, and accessibility changes with Breaking/NonBreaking severity.
- **find_reflection_usage** — Detect dynamic/reflection-based usage
- **find_references** — Find all references to any symbol (types, methods, properties, fields, events)
- **go_to_definition** — Find the source file and line where a symbol is defined
- **get_diagnostics** — List compiler errors, warnings, and Roslyn analyzer diagnostics
- **get_code_fixes** — Get available code fixes with structured text edits for any diagnostic
- **search_symbols** — Fuzzy workspace symbol search by name
- **get_nuget_dependencies** — List NuGet package references per project
- **find_attribute_usages** — Find types and members decorated with a specific attribute
- **find_obsolete_usage** — Every `[Obsolete]` call site grouped by deprecation message and severity, errors first; for planning migrations
- **find_circular_dependencies** — Detect cycles in project or namespace dependency graphs
- **get_complexity_metrics** — Cyclomatic complexity analysis per method
- **find_naming_violations** — Check .NET naming convention compliance
- **find_async_violations** — Sync-over-async, `async void` misuse, missing awaits, fire-and-forget tasks; per-violation report with severity
- **find_disposable_misuse** — `IDisposable`/`IAsyncDisposable` instances not wrapped in `using`/`await using`/returned/assigned to field; severity error/warning per violation.
- **find_large_classes** — Find oversized types by member or line count
- **find_god_objects** — Types combining high size with high cross-namespace coupling; sharper signal than raw size for SRP violations
- **find_unused_symbols** — Dead code detection via reference analysis. Auto-filters test methods (xUnit/NUnit/MSTest), MCP tool entry points, source-generator output, MEF-composed services, and interop-laid-out fields; filter counts surface in `summary.filteredOut`
- **get_project_health** — Composite audit aggregating 7 quality dimensions per project (complexity, large classes, naming, unused symbols, reflection, async violations, disposable misuse) with counts and top-N hotspots inline
- **get_source_generators** — List source generators and their output per project
- **get_generated_code** — Inspect generated source code from source generators
- **inspect_external_assembly** — Browse types, members, and XML docs from closed-source NuGet packages and referenced assemblies
- **peek_il** — Decompile any method to ilasm-style IL bytecode from closed-source or generated assemblies
- **get_code_actions** — Discover available refactorings and fixes at any position (extract method, rename, inline variable, and more)
- **apply_code_action** — Execute any Roslyn refactoring by title, with preview mode (returns a diff before writing to disk)
- **list_solutions** — List all loaded solutions and which one is currently active
- **set_active_solution** — Switch the active solution by partial name (all subsequent tools operate on it)
- **load_solution** — Load an additional .sln/.slnx at runtime and make it the active solution
- **unload_solution** — Unload a loaded solution to free memory
- **rebuild_solution** — Force a full reload of the analyzed solution
- **start_background_task** — Queue a long-running tool (currently `rebuild_solution`) to run in the background; returns a `taskId` to poll
- **get_task_status** — Get the current status, result, or error of a background task by its `taskId`
- **list_running_tasks** — List background tasks running or completed within the last 5 minutes
- **trust_solution** — Authorize a solution to run Roslyn analyzers (required before `get_diagnostics` with `includeAnalyzers: true`)
- **list_trusted_paths** — Inspect the persistent trust store + session-trusted solutions
- **revoke_trust** — Revoke a previously-granted trust for a solution path
- **analyze_data_flow** — Variable read/write/capture analysis within a statement range (declared, read, written, always assigned, captured, flows in/out)
- **analyze_control_flow** — Branch/loop reachability analysis within a statement range (start/end reachability, return statements, exit points)
- **analyze_change_impact** — Show all files, projects, and call sites affected by changing a symbol — combines find_references and find_callers
- **get_type_overview** — Compound tool: type context + hierarchy + file diagnostics in one call
- **analyze_method** — Compound tool: method signature + callers + outgoing calls in one call
- **get_overloads** — Every overload of a method/constructor (source + metadata) with full parameter and modifier detail in one call
- **get_operators** — Every user-defined operator and conversion operator on a type (source + metadata) with kind, signature, parameters, and source location. Includes synthesized record equality and .NET 7+ checked variants
- **get_call_graph** — Transitive caller/callee graph for a method, depth-bounded with cycle detection
- **get_file_overview** — Compound tool: types defined in a file + file-scoped diagnostics in one call

## Response shape

All list-returning tools wrap their results in a uniform envelope:

```json
{
  "items": [ ... ],
  "totalCount": 142,
  "truncated": false,
  "limit": 500,
  "summary": { ... }
}
```

When `truncated` is `true`, the items are the **top N by the tool's natural sort order** (severity-first, worst-first, by-project, etc.) — usually that's exactly what you want. Raise `limit` only if the missing tail items matter for the task.

Tools that include a `summary` aggregate today:

- `get_diagnostics` — `{ error, warning, info, hidden }` counts
- `find_references`, `find_callers`, `find_attribute_usages` — `{ byProject: { name: count } }`
- `search_symbols`, `find_reflection_usage` — `{ byKind: {...} }`
- `find_unused_symbols` — `{ byKind, filteredOut: { testMethod, testContainer, mcpTool, generated, composition, interop } }`
- `find_naming_violations` — `{ byRule: {...} }`
- `get_complexity_metrics` — `{ max, avg, overThreshold }`

Single-object tools (`get_type_overview`, `get_symbol_context`, `apply_code_action`, etc.) return their bespoke shape directly — the envelope only wraps list-returning tools.

## Error responses

When a tool can't proceed (symbol not resolved, solution not trusted, file not found, ambiguous match, etc.), the response is an `isError: true` content block carrying a structured JSON body:

```json
{
  "code": "SolutionNotTrusted",
  "message": "Solution 'Foo.sln' is not trusted for analyzer execution. ...",
  "details": { "solutionPath": "C:\\Foo.sln" }
}
```

Error codes (switch on `code` to handle each):

- `SymbolNotFound` — type / method / property could not be resolved.
- `SolutionNotTrusted` — `get_diagnostics` or `get_code_f