roslyn-mcp-server

Roslyn-backed MCP server for AI agents working with .NET solutions.

The project provides a sync-aware semantic layer over MSBuildWorkspace, so MCP clients can:

• load a solution explicitly
• inspect projects and source files
• navigate symbols and references
• query diagnostics and semantic relationships
• keep workspace state aligned with external file edits

The server targets .NET 9 and supports both stdio and HTTP transports.

What it does

The current implementation is focused on read-only Roslyn tooling for agent workflows.

Workspace and server tools

• server_info Returns basic server and runtime information.
• workspace_context Resolves workspace context from an explicit solutionPath.
• diagnose Checks environment readiness, MSBuild availability, and solution load health.
• load_solution Loads a .sln, .slnx, or .csproj into a live Roslyn workspace.
• get_workspace_state Returns the currently loaded workspace state and cached solution summaries.
• get_project_structure Returns projects and, optionally, source documents for a loaded solution.

Navigation tools

• get_document_outline Returns a structural outline of a C# source file.
• get_file_overview Returns a compact overview of a source file, including its main declarations.
• get_type_overview Returns a compact overview of a resolved type.
• get_type_members Returns members declared on the resolved type.
• search_symbols Searches source declarations across the loaded solution.
• get_symbol_info Resolves semantic symbol information at a file position.
• get_symbol_attributes Returns attributes applied to the resolved symbol.
• go_to_definition Returns source definition locations for the resolved symbol.
• get_method_signature Returns the signature of a callable member at a file position.
• get_method_source Returns the source body of a callable member at a file position.
• find_references Finds source references for the resolved symbol.

Analysis tools

• get_diagnostics Returns compiler diagnostics for a solution or a specific file.
• validate_code Returns a lightweight validity summary based on compiler diagnostics.
• find_implementations Finds implementations of interfaces, abstract types, and virtual members.
• get_type_hierarchy Returns base types, derived types, and interfaces for a resolved type.
• find_callers Finds caller locations for callable symbols.
• get_outgoing_calls Returns outgoing call edges for a callable member.
• analyze_method Returns method-level data flow, control flow, signature, and outgoing call information.
• analyze_change_impact Returns a best-effort impact summary for a symbol, including references and implementations.
• check_type_compatibility Checks whether two resolved types are compatible.

Workspace synchronization

The server is designed for long-running agent sessions where files may change outside the Roslyn API.

It maintains a live workspace synchronization pipeline that:

• watches workspace files for external changes
• updates Roslyn documents incrementally when possible
• reloads the workspace when project structure changes require it
• ensures semantic queries use the current Workspace.CurrentSolution

In practice, this means tools such as find_references, analyze_method, and get_diagnostics can reflect edits made:

• by the user in an IDE
• by an agent through direct file edits
• by other tooling that changes files on disk

Running the server

Build the solution:

dotnet build .\roslyn-mcp-server.sln -v minimal

Run the stdio host:

dotnet run --project .\src\RoslynMcpServer.Host.Stdio\RoslynMcpServer.Host.Stdio.csproj

Run the HTTP host:

dotnet run --project .\src\RoslynMcpServer.Host.Http\RoslynMcpServer.Host.Http.csproj -- --urls http://localhost:3001

HTTP host

The HTTP host exposes:

• `GE

... View full README on GitHub