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Quick Start

The fastest way to create a widget: 
fastapps create mywidget
This creates:
  • server/tools/mywidget_tool.py - Python backend logic
  • widgets/mywidget/index.jsx - React frontend component

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Widget Architecture

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Core Concepts

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1. Data Flow

MCP Tool → window.openaiThe MCP tool returns toolOutput and metadata, which are stored inside window.openai.
window.openai → React ComponentThe component reads data (like tool input/output, theme, layout) from window.openai using hooks such as useWidgetProps or useOpenAiGlobal.
React Component → useWidgetStateUser interactions (clicks, filters, toggles) are handled in React and synchronized with the host through useWidgetState.
useWidgetState → window.openai.setWidgetStateWhen state changes, it’s sent to the host via window.openai.setWidgetState() for persistence.
window.openai → ChatGPT Host ContextChatGPT stores the widget state persistently, so it’s available across sessions and visible to the model for reasoning.

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2. File Structure

widgets/
  mywidget/
    index.jsx          # React component
server/tools/
  mywidget_tool.py     # Python backend

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3. React Hooks

  • useWidgetProps() - Access tool output data
  • useWidgetState() - Manage persistent state
  • useOpenAiGlobal() - Access ChatGPT environment
  • useDisplayMode() / useMaxHeight() - Layout convenience hooks

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Next steps

Ready to start building?
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