# Roslyn Mcp Server > MCP server that gives AI agents Roslyn-backed navigation, references, hover, and diagnostics for large C#/.NET repositories. - **Type:** MCP server - **Install:** `agentstack add mcp-kirnot92-roslyn-mcp-server` - **Verified:** Yes — security-reviewed for prompt injection and unsafe behavior - **Seller:** [kirnot92](https://agentstack.voostack.com/s/kirnot92) - **Installs:** 0 - **Category:** [Integrations](https://agentstack.voostack.com/c/integrations) - **Latest version:** 0.1.0 - **License:** MIT - **Upstream author:** [kirnot92](https://github.com/kirnot92) - **Source:** https://github.com/kirnot92/roslyn-mcp-server ## Install ```sh agentstack add mcp-kirnot92-roslyn-mcp-server ``` Requires the [AgentStack CLI](https://agentstack.voostack.com/docs/cli). Works with Claude Code, Cursor, and any MCP-compatible agent. ## About # roslyn-mcp-server `roslyn-mcp-server` is an unofficial C# MCP server that lets AI agents use Roslyn language features through `roslyn-language-server`. The server is meant for Agent CLI-style tools working inside real C# repositories, including large mono-repos. It runs as an MCP stdio server, starts `roslyn-language-server` as a child LSP process after a solution or project is selected, then translates MCP tool calls into LSP requests. The main goal is not to replace an IDE. The goal is to give an agent enough compiler-backed context to read, review, and navigate C# code without forcing the agent to parse a large repository by itself. ## Why This Exists AI agents can inspect files with normal filesystem tools, but C# code often needs semantic context: - where a symbol is defined - which overload or type a reference points to - where a symbol is referenced - what diagnostics Roslyn currently knows about - what symbols are present in a file or workspace Roslyn already knows how to answer these questions. This project provides a thin MCP bridge so an agent can ask those questions while it works. ## Large Repository Design The project assumes large repositories from the beginning. A useful agent tool must stay predictable even when a repo has hundreds of projects, many solutions, slow restore state, or partial Roslyn indexing. That leads to a few design choices: - By default the server does not load a solution at startup; `--load-solution` can opt into early solution loading. - Workspace discovery is bounded by scan depth, timeout, and candidate limits. - If multiple `.sln`, `.slnx`, or `.csproj` files exist, the agent must choose. - Roslyn LS is launched only after `load_solution`, `load_project`, or an unambiguous first read-tool auto-load. - Read tools do not block indefinitely while the language server is warming. - Large result sets are capped and report `totalKnown`, `returned`, and `truncated` metadata. - Warming or partially loaded workspaces return best-effort results with `workspaceState`, `completeness`, and retry metadata. - Diagnostics are based on `textDocument/publishDiagnostics` notifications already processed by the bounded background diagnostics queue; the server does not run an unbounded workspace-wide diagnostic computation. Queue capacity and pending/processed/dropped/stale counts are exposed through `get_workspace_status`. In practice, `WorkspaceWarming` is a normal state for large repositories. Agents should use partial results when they are good enough and call `get_workspace_status` when they need to understand load warnings or failures. ## Implemented Tools Workspace tools: - `list_workspaces` - Discover `.sln`, `.slnx`, and `.csproj` candidates under the workspace root. Optional `maxDepth` skips git-based discovery and performs bounded filesystem BFS for near-root workspace files. - `load_solution` - Load a selected `.sln` or `.slnx` into Roslyn LS. - `load_project` - Load a selected `.csproj` into Roslyn LS. - `get_workspace_status` - Report the selected target, load state, warnings, open documents, and diagnostics queue/cache status. Read-only Roslyn tools: - `document_symbols` - Return file-level types, members, and symbol ranges, optionally filtering returned symbols by kind while preserving ancestor context for matching descendants. - `hover` - Return Roslyn hover text for a source position. - `go_to_definition` - Return definition locations for a source position. - `peek_definition` - Return definition locations plus bounded source snippets. - `find_references` - Return references for a source position. - `peek_references` - Return reference locations plus bounded source snippets. - `find_implementations` - Return implementation locations from an interface, abstract member, or base contract position. Calling it on a concrete implementation may legitimately return only that implementation. Results can be narrowed with root-relative `includePathPrefixes`. - `get_call_hierarchy` - Return direct depth-1 incoming callers, outgoing callees, or both for a method, constructor, or property accessor position, optionally filtering returned edge counterparts by kind: `method`, `constructor`, `property`, `event`, `operator`, or `field`, and by root-relative `includePathPrefixes`. - `get_type_hierarchy` - Return base type, derived type, or interface implementation hierarchy edges for a type position, with bounded breadth-first traversal depth, result caps, and optional root-relative `includePathPrefixes`. - `find_symbols` - Search workspace symbols by name, optionally filtering returned results by kind such as `class`, `interface`, `method`, `property`, or `field`, and by symbol-name `matchMode`: `default`, `exact`, `prefix`, or `contains`. Default matching keeps Roslyn LS fuzzy candidates but ranks exact, prefix, and contains name matches before the result cap. It can also keep only symbols located under root-relative `includePathPrefixes`, which is useful in large repositories. - `diagnostics` - Return currently known file or workspace diagnostics. Resources: - `roslyn://server/guide` - Short usage guidance for agents. - `roslyn://server/capabilities` - Short read-only capability summary. This project is intentionally read-only. Rename, code actions, formatting, and apply/edit tools are outside the product direction; agents should make file changes with their normal workspace editing tools after using Roslyn context to understand the code. ## Getting Started Prerequisites: - .NET 10 SDK for installing .NET tools - `roslyn-language-server` Install `roslyn-language-server` separately: ```text dotnet tool install --global roslyn-language-server --prerelease ``` `roslyn-mcp-server` does not bundle Roslyn LS. Starting with v0.4.0, the .NET tool package ID is `Kirnot.RoslynMcpServer`; the installed command remains `roslyn-mcp-server`. ### .NET Tool Install the MCP server as a .NET global tool: ```text dotnet tool install --global Kirnot.RoslynMcpServer ``` Run the installed command: ```text roslyn-mcp-server --help ``` If your MCP client does not inherit the .NET global tools directory on `PATH`, point it at the tool shim directly: ```text %USERPROFILE%\.dotnet\tools\roslyn-mcp-server.exe ``` On macOS or Linux: ```text $HOME/.dotnet/tools/roslyn-mcp-server ``` ### Release Artifacts Alternatively, download the self-contained artifact for your OS from the [v0.4.0 release](https://github.com/kirnot92/roslyn-mcp-server/releases/tag/v0.4.0) or the [latest release](https://github.com/kirnot92/roslyn-mcp-server/releases/latest): - `roslyn-mcp-server-v0.4.0-win-x64.zip` - `roslyn-mcp-server-v0.4.0-linux-x64.tar.gz` - `roslyn-mcp-server-v0.4.0-osx-x64.tar.gz` - `roslyn-mcp-server-v0.4.0-osx-arm64.tar.gz` The release artifacts are self-contained and single-file. The server executable does not require a separate .NET runtime installation, though `roslyn-language-server` and the target C# repository still need a compatible .NET SDK/runtime environment. Point your MCP client at the extracted executable: ```text C:\Tools\roslyn-mcp-server\roslyn-mcp-server.exe ``` On macOS or Linux, extract the `.tar.gz` and use the `roslyn-mcp-server` executable from the extracted folder. If your archive tool does not preserve the executable bit, run `chmod +x roslyn-mcp-server`. ### Build From Source Use source builds for local development, unsupported platforms, or if you want to run the server directly from this repository. Source builds require Git and the .NET 10 SDK. ```powershell git clone https://github.com/kirnot92/roslyn-mcp-server.git cd roslyn-mcp-server dotnet build .\src\RoslynMcpServer\RoslynMcpServer.csproj -c Release ``` The built server executable will be under: ```text src/RoslynMcpServer/bin/Release/net10.0/ ``` On Windows, the executable is typically: ```text src/RoslynMcpServer/bin/Release/net10.0/roslyn-mcp-server.exe ``` On macOS or Linux, the executable is typically: ```text src/RoslynMcpServer/bin/Release/net10.0/roslyn-mcp-server ``` After installing, downloading, or building the server, configure your MCP client to run `roslyn-mcp-server` or the server executable from the repository root you want to inspect. If you prefer a self-built release-style layout, publish instead of building. Use the runtime identifier for your target platform, such as `win-x64`, `linux-x64`, `osx-x64`, or `osx-arm64`: ```powershell git clone https://github.com/kirnot92/roslyn-mcp-server.git cd roslyn-mcp-server dotnet publish .\src\RoslynMcpServer\RoslynMcpServer.csproj -c Release -r win-x64 --self-contained true -p:PublishSingleFile=true -p:IncludeNativeLibrariesForSelfExtract=true -p:DebugType=None -p:DebugSymbols=false -o .\publish\roslyn-mcp-server ``` With the default configuration, the current working directory becomes the workspace root. Use `--root ` only when your MCP client cannot set the working directory. Use `--roslyn-language-server ` only when `roslyn-language-server` is not on `PATH`. `--load-solution ` is optional. When set, the server starts loading that `.sln` or `.slnx` as soon as the MCP server starts, so Roslyn LS can warm while the agent reads the repository. When it is omitted, the agent can still call `load_solution` or `load_project` when it needs Roslyn context. Recommended tool flow: 1. `list_workspaces` 2. `load_solution` or `load_project` 3. `get_workspace_status` 4. read-only Roslyn tools For code review workflows, start workspace loading early. A good pattern is to inspect the changed file list, load the intended solution or project, then read the diff while Roslyn LS warms in the background. ## MCP Client Setup Install, download, or build the server first, then point your MCP client at `roslyn-mcp-server` or the server executable. Use `cwd` or `--root ` so the server knows which repository to inspect. Solution paths passed to `--load-solution` must be the exact root-relative path, such as `Sources/Server.sln`, or an absolute path inside the root. The server does not recursively search for a matching file name from this option. ### 1. Claude Code Local setup with `claude mcp add`: ```powershell claude mcp add --transport stdio roslyn -- ` roslyn-mcp-server ` --root ` --load-solution Server.sln ``` Project-scoped `.mcp.json`: ```json { "mcpServers": { "roslyn": { "command": "roslyn-mcp-server", "args": ["--root", ".", "--load-solution", "Server.sln"] } } } ``` ### 2. Gemini CLI Project `.gemini/settings.json`: ```json { "mcpServers": { "roslyn": { "command": "roslyn-mcp-server", "args": ["--load-solution", "Server.sln"], "cwd": "", "timeout": 30000 } } } ``` ### 3. Codex Global `~/.codex/config.toml`, or project-scoped `.codex/config.toml` in a trusted project: ```toml [mcp_servers.roslyn] command = "roslyn-mcp-server" args = ["--root", "", "--load-solution", "Server.sln"] ``` If you keep a project-scoped `.codex/config.toml` in the repository root, `--root` can usually be `.`: ```toml [mcp_servers.roslyn] command = "roslyn-mcp-server" args = ["--root", ".", "--load-solution", "Server.sln"] ``` ### Multiple Solutions For repositories with separate solutions, run separate MCP server entries. For example, a Unity project can expose both server and client solutions: ```json { "mcpServers": { "roslyn-server": { "command": "roslyn-mcp-server", "args": ["--load-solution", "Server.sln"], "cwd": "" }, "roslyn-unity": { "command": "roslyn-mcp-server", "args": ["--load-solution", "UnityClient.sln"], "cwd": "" } } } ``` More setup and client examples are in [docs/usage.md](docs/usage.md). ## Current Status The project is pre-release but usable for read-only C# navigation and diagnostics in agent workflows. It has been smoke-tested with real repositories including PowerShell, Semantic Kernel, and ASP.NET Core. Those tests are intentionally about responsiveness and usable metadata, not perfect semantic completeness for every large solution. Known constraints: - `roslyn-language-server` is a prerelease dependency and may change behavior. - Large repositories may remain in `WorkspaceWarming` for a long time. - Project load errors usually reflect local SDK, workload, restore, or `global.json` environment problems and are surfaced through workspace warnings. - Diagnostics are current-known diagnostics from the last processed `textDocument/publishDiagnostics` notifications, not a guaranteed full build result. - Write/refactoring tools are not implemented. Implementation notes for maintainers are in [AGENTS.md](AGENTS.md) and [docs/implementation-notes.md](docs/implementation-notes.md). ## License This project is licensed under the MIT License. See [LICENSE](LICENSE) for details. ## Source & license This open-source MCP server is cataloged on AgentStack and links to its original source — we do not rehost the code. - **Author:** [kirnot92](https://github.com/kirnot92) - **Source:** [kirnot92/roslyn-mcp-server](https://github.com/kirnot92/roslyn-mcp-server) - **License:** MIT Install and usage instructions live in the source repository linked above. ## Pricing - **Free** — Free ## Security capabilities Automated source analysis of v0.1.0 — what this tool can access: - **Network access:** no - **Filesystem access:** no - **Shell / process execution:** no - **Environment & secrets:** no - **Dynamic code execution:** no *"Yes" means the capability is present in the source — more access means more to trust, not that it is unsafe.* ## Versions - **0.1.0** — security scan: passed — Imported from the upstream source. ## Links - Listing page: https://agentstack.voostack.com/l/mcp-kirnot92-roslyn-mcp-server - Seller: https://agentstack.voostack.com/s/kirnot92 - Browse the marketplace: https://agentstack.voostack.com/browse --- Listed on AgentStack — the marketplace for AI agent skills and MCP servers. Every listing is security-reviewed. Creators keep 70%.