ToolBox Architecture — VS Code Extension

How the Power Platform ToolBox VS Code Extension is structured, and how it hosts tools inside VS Code webviews.

Overview

The extension follows a two-part architecture common to VS Code extensions: an extension host process (Node.js, runs in the background) and one or more webviews (Chromium-based, render UI), communicating over VS Code's postMessage bridge.

Extension Host

Source lives under src/:

Name
extension.ts
Description
Entry point — activates the extension, registers commands, views, and panels.
Name
managers/
Description
Business logic: connections, tool installation, marketplace, settings.
Name
panels/
Description
Webview panel wrappers — connectionPanel.ts, cspPermissionsPanel.ts, toolHostPanel.ts, toolPanel.ts.
Name
providers/
Description
Tree data providers for the Activity Bar views (connections, installed tools, marketplace).
Name
registrations/
Description
Command registrations (pptb.tools.launch, pptb.connections.connect, etc.).
Name
statusbar/
Description
Status bar items (e.g. active connection indicator).
Name
polyfill/toolboxAPI.js
Description
The toolboxAPI runtime injected into each tool's webview.

Webview UI

Source lives under webviews/, written in React/TypeScript:

connection/ — connection management UI
toolHost/ — hosts the list of installed/marketplace tools and launches them
toolTool/ — renders an individual tool inside its own webview

Tool Bridge

A tool calls window.toolboxAPI.* the same way it would in the Desktop App. The polyfill/toolboxAPI.js runtime translates each call into an invoke() message sent via postMessage to toolPanel.ts in the extension host, which handles it in a command switch and posts the result back.

Current Parity Notes

The extension implements most of the Desktop App's tool-facing surface, but a few capabilities are still rolling out. See the Feature Comparison table in the vscode-extension repo for the full breakdown. Notably, toolPanel.ts currently throws "Tool invocation is not yet available in VS Code host." for launchTool() — Inter-Tool Invocation, Agent Integration (MCP), headless invocation, and the standalone CLI are Desktop-only today. These are flagged with a

Desktop only

badge throughout the Tool Development docs.