VSCode MCP Server

MCP Server Integration:Built using the MCP TypeScript SDK (@modelcontextprotocol/sdk), the extension instantiates an MCP server that registers diagnostic tools and handles MCP protocol messages.

Diagnostic Tool (code_checker):The registeredcode_checkertool collects diagnostics from VSCode’s built-in language services, filtering out files without errors. When invoked, it returns a formatted JSON object containing diagnostic information (only for files with issues).

Focus Editor Tool (focus_editor): Opens a specific file in the VSCode editor and navigates to a designated line and column. Useful for bringing files into visual focus for the user but does not include file content in the tool call result.

Search Symbol Tool (search_symbol): Searches for symbols in the workspace, using "Go to Definition" primarily, with a fallback to text search (similar to Ctrl+Shift+F). Can optionally open the results in the editor using thefocus_editortool.

Debug Session Management Tools:The extension provides tools to manage VSCode debug sessions directly using MCP:

- list_debug_sessions: Retrieve all active debug sessions in the workspace.
- start_debug_session: Start a new debug session with the provided configuration.
- stop_debug_session: Stop debug sessions matching a specific session name.
- restart_debug_session: Restart a debug session by stopping it and then starting it with the provided configuration (new!).

SSE Communication:An Express-based HTTP server runs on a configurable port (default: 6010) and dynamically handles port conflicts. It exposes:

- AGET/sseendpoint to establish a long-lived Server-Sent Events (SSE) connection. If the default port (6010) is unavailable, users can configure a new one via their VSCode settings (see Dynamic Port Configuration below).
- APOST/messagesendpoint for receiving MCP messages from external clients (such as your AI assistant). Special care is taken to handle the request body properly—thanks to passing the already-parsedreq.bodyto avoid stream-related errors.

Verbose Logging:All activity, including server startup, SSE connection status, and message handling events, is logged to an output channel named"VSCode MCP Server"to aid debugging and transparency.

Using the Extension from Claude Desktop (MCP Client)

To use the VSCode MCP Server with Claude Desktop, you need to configure Claude Desktop to connect to the MCP server running in VSCode. Since the implementation of the MCP server uses SSE transport, and Claude Desktop only supports stdio transport, you need to use amcp-proxyto bridge the communication between the two.

{ "mcpServers": { "vscode": { "command": "mcp-proxy", "args": ["http://127.0.0.1:6010/sse"] } } }

- Youmustrestart Claude Desktop for the changes to take effect by using theFile>Exitoption.
- NOTE: This is different than just closing the window or usingFile>Close, which leaves the application running in the background.
- After existing and then starting again, Claude Desktop should now be able to connect to the MCP server running in VSCode.

The MCP Server status can now be managed directly from the Command Palette:
- Stop MCP Server(mcpServer.stopServer): Stops the currently running MCP Server.
- Start MCP Server(mcpServer.startServer): Starts the server on the configured or next available port.

These commands help manage server lifecycle dynamically, without requiring a VSCode restart.

If the port is already in use, the extension will suggest the next available port and apply it dynamically. Logs reflecting the selected port can be found in theMCP Server Logsoutput channel.

Users can configure or change the MCP Server's port at runtime using the Command Palette:
- Open the Command Palette (Ctrl+Shift+PorCmd+Shift+Pon macOS).
- Search forSet MCP Server Port.
- Enter the desired port number in the input box and confirm.

The server will dynamically restart on the newly selected port, and the configuration will be updated for future sessions.

The HTTP server port can also be set via VSCode settings:
- Open VSCode settings (File > Preferences > SettingsorCtrl+,).
- Search formcpServer.port.
- Set your desired port number.
- Restart VSCode for the changes to take effect.

The MCP Server starts automatically on VSCode activation by default. To disable this feature:
- Open VSCode settings (File > Preferences > SettingsorCtrl+,).
- Search formcpServer.startOnActivate.
- Toggle the setting tofalse.

This can be useful if you prefer to start the server manually using theStart MCP Servercommand.

Steps for developing and debugging the extension, source code available atGitHub.
-

git clone https://github.com/microsoft/semanticworkbench.git

cd semanticworkbench/mcp-servers/mcp-server-vscode