Roslyn Codelens Mcp

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.

Hosted deployment

A hosted deployment is available on Fronteir AI.

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. Reads generic (AddSingleton<IFoo, Foo>()), single-generic, typeof pair and factory-lambda forms
• get_instantiation_options — "How do I construct this type?" in one call: constructors with full parameter detail, static factory methods declared anywhere in the solution (including on a separate factory type), DI registrations, and required members. Pass fromProject to learn whether that project can actually reach each option — it honours InternalsVisibleTo, so it answers "can my test project call this internal constructor?"
• 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
• get_exception_flow — What exceptions can escape a method: walks callees depth-bounded, propagates each throw up through every enclosing try/catch, and reports what still escapes with its propagation path; metadata callees contribute their documented exceptions
• find_throw_sites — Every place an exception type is thrown, optionally including derived types; rethrows flagged
• find_catch_blocks — Every catch for a type, optionally via base clauses; flags filtered, rethrowing, and empty (swallowing) handlers
• find_references — Find all references to any symbol (types, methods, properties, fields, events), each tagged with a kind (read, write, readwrite, invocation, method_group, object_creation, cast, type_check, typeof, base_type, type_constraint, type_argument, declaration, attribute, nameof, xml_doc) and reported per occurrence with a column; filter server-side with kinds (e.g. ["write","readwrite"] for mutation sites)
• go_to_definition — Find the source file and line where a symbol is defined
• get_method_source — Full declaration source (XML docs, attributes, signature, body — original