Pixie Apps SDK

What it does

Pixie Apps SDK is a developer library that abstracts the differences between OpenAI's ChatGPT Apps and Anthropic's MCP Apps platforms. Build your interactive widget once with window.pixie and it automatically detects which platform it's running on — Claude Desktop, VS Code Copilot, or ChatGPT — and initialises accordingly.

Key features

• Cross-platform — one codebase targets both OpenAI Apps and MCP Apps without conditional logic
• React hooks — useToolInput, useToolOutput, useTheme, useDisplayMode and more for reactive widget development
• Widget state persistence — getWidgetState/setWidgetState for state that survives re-renders
• Tool calling from widgets — call MCP tools directly from your widget UI
• Display mode control — request PiP, inline, or fullscreen modes programmatically

Installation

npm install pixie-apps-sdk

Then import once in your widget entry point:

import 'pixie-apps-sdk';
// window.pixie is now available everywhere

Supported hosts

Claude Desktop (MCP Apps), ChatGPT (OpenAI Apps) — any host that supports MCP Apps or OpenAI App extensions