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FastApps is the most effective and fast way to build Apps in ChatGPT, utilizing the FastMCP framework specialized for the apps sdk. Here’s a simple Hello World widget to show how easy it is: Python Backend (server/tools/hello_tool.py) 
from fastapps import BaseWidget, Field
from pydantic import BaseModel

class HelloInput(BaseModel):
    name: str = Field(default="World", description="Name to greet")

class HelloTool(BaseWidget):
    identifier = "hello"
    title = "Hello Widget"
    input_schema = HelloInput
    
    async def execute(self, input_data: HelloInput):
        return {
            "message": f"Hello, {input_data.name}!",
            "emoji": "👋"
        }
React Frontend (widgets/hello/index.jsx) 
import React from 'react';
import { useWidgetProps } from 'fastapps';

export default function HelloWidget() {
  const props = useWidgetProps();
  
  return (
    <div>
      <h1>Hello world!</h1>
    </div>
  );
}

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Key Features

FastApps provides everything you need to build sophisticated ChatGPT apps: Widget Registration: Use the BaseWidget class to simply register it as an MCP tool. We handle the rest - no complex configuration or manual registration needed. CLI commands: Just type fastapps init to set up the whole project. Use fastapps create mywidget to make an widget. Everything from component creation to MCP tool registeration will be set up automatically. Simple auth: Authentication and other advanced features are all handled with our simple decorators. Just add @auth_required and you’re done.

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Solutions We Provide

FastApps solves the three biggest challenges in building ChatGPT apps: Complex setup: Traditional approaches require extensive boilerplate, manual registration, and complex build systems. FastApps eliminates all of this with a simple two-file structure and automatic discovery. State management: Managing persistent state across ChatGPT sessions is complex. We’ve transformed OpenAI’s Apps SDK functions into a clean library. Simply import and use hooks like useWidgetProps(), useWidgetState(), and useOpenAiGlobal() without dealing with the raw SDK complexity. API integration: Connecting to external APIs while handling security policies and data flow is challenging. FastApps handles CSP configuration and provides a clean data flow from Python to React.

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Getting Started

Ready to build your first widget? Follow our step-by-step guide:
  1. Install FastApps: pip install fastapps
  2. Create a project: fastapps init my-app
  3. Generate a widget: fastapps create my-widget
Check out our Getting Started Guide for a complete walkthrough, or explore our examples gallery to see real-world applications.

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Architecture

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What Makes FastApps Different?

Most frameworks force you to deal with:
  • ❌ Complex project configuration
  • ❌ Manual widget registration
  • ❌ Boilerplate setup code
  • ❌ Build system configuration
FastApps eliminates all of that:
  • ✅ Auto-discovery: Widgets are automatically found and registered
  • ✅ Only two files per widget: One Python file, one React file. That’s it.
  • ✅ CLI scaffolding: Generate widgets instantly
  • ✅ Type-safe: Pydantic for Python, TypeScript for React
  • ✅ Apps SDK hooks support: Use hooks like useWidgetProps() and useWidgetState()

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Next Steps

Now that you understand what FastApps is, explore these topics:
  1. Introduction - Learn about the framework architecture
  2. Quick Start - Get up and running in minutes
  3. Building Widgets - Create your first interactive component
  4. Server - Develop Python backends for your widgets
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