ChatGPT Apps SDK Tutorial: From Zero to Production
The OpenAI Apps SDK, announced at DevDay 2025, introduces a revolutionary way to extend ChatGPT's capabilities. Built on the Model Context Protocol (MCP) open standard, the Apps SDK enables developers to create apps that integrate seamlessly into ChatGPT conversations.
What are ChatGPT Apps?
The Model Context Protocol (MCP)
ChatGPT apps are intelligent extensions that appear naturally in conversation. Unlike traditional plugins or webhooks, apps are suggested by ChatGPT at contextually appropriate moments or can be invoked by name. They respond to natural language and provide interactive interfaces directly within the chat experience.
- Interoperability: Apps built on MCP can potentially work across different AI platforms
- Community Support: Open standards benefit from wider community contributions and tooling
- Future-Proofing: Standards-based development protects your investment as the ecosystem evolves
- Transparency: Open protocols enable better security auditing and trust
The Apps SDK is built on MCP, an open standard for AI-application integration. This architectural choice provides several advantages:
Setting Up Your Development Environment
Before building your first app, you'll need to set up your development environment. Start by signing up for an OpenAI developer account at platform.openai.com. Enable Developer Mode in your ChatGPT settings to test apps before publication. Install the Apps SDK using npm or your preferred package manager. Review the Apps SDK documentation and sample code.
Building Your First App: A Weather Assistant
Let's create a simple but functional weather app that responds to natural language queries about current conditions and forecasts.
The app manifest describes your app's capabilities, the data it needs, and how ChatGPT should invoke it. Include your app's name and description, required permissions and scopes, API endpoints for different functions, and authentication requirements.
Step 1: Define Your App Manifest
Your app needs to implement several MCP methods to function correctly. The discovery endpoint tells ChatGPT what your app can do. Context handlers receive and process information from the conversation. Action handlers execute specific functions when invoked. Response formatters structure data for display in chat.
Step 2: Implement the MCP Interface
One of the most powerful features of ChatGPT apps is their access to conversation context. Your app receives relevant context about the ongoing conversation, user preferences and historical interactions, location information (with user permission), and related data from other apps in the conversation.
Step 3: Handle Context and State
Use this context intelligently to provide better experiences. For example, if the user asked about weather in Paris earlier, your app might default to Paris for subsequent queries without requiring explicit repetition.
Step 4: Design the User Interface
For our weather app, we might show current conditions as formatted text with an icon, a 5-day forecast as an interactive chart, and severe weather alerts as highlighted callouts.
Apps can provide rich interactive interfaces within ChatGPT. The Apps SDK supports formatted text with markdown, interactive buttons and forms, charts and visualizations, images and media, and maps and location data.
Enable Developer Mode in ChatGPT to test your app before submitting it for review. Developer Mode allows you to load apps locally, see detailed logs and debugging information, test different scenarios and edge cases, and iterate rapidly without deployment delays.
Step 5: Testing with Developer Mode
Respond quickly—users expect near-instant results in conversation. Handle errors gracefully and provide helpful messages. Respect user privacy and be transparent about data usage. Make your app discoverable with clear descriptions. Design for conversation, not traditional UI paradigms. Test across different contexts and conversation flows.
Best Practices
Publishing Your App
Once you've built and thoroughly tested your app, you can submit it for review. OpenAI will evaluate apps for quality, security, and compliance with guidelines. Later in 2025, OpenAI will open app submissions and provide details about monetization opportunities.
Next Steps
Explore the example apps in the Apps SDK documentation. Join the OpenAI developer community to share learnings. Consider integrating your existing services as ChatGPT apps. Think about unique capabilities that conversational AI enables.
The Apps SDK represents a new paradigm for application development—one where natural language is the primary interface and context is automatically managed. Get started today and be part of shaping this ecosystem.