building-chatgpt-apps
Guides creation of ChatGPT Apps with interactive widgets using OpenAI Apps SDK and MCP servers. Use when building ChatGPT custom apps with visual UI components, embedded widgets, or rich interactive experiences. Covers widget architecture, MCP server setup with FastMCP, response metadata, and Developer Mode configuration. NOT when building standard MCP servers without widgets (use building-mcp-servers skill instead).
npx skills add majiayu000/claude-skill-registry --skill building-chatgpt-apps-abdullahmalik17-digital-fte-2 --agent claude-code
Same command for any agent — swap --agent for codex, cursor, copilot.
Weekly change comes from our own snapshots, not the repository page — it measures attention, not adoption.
# ChatGPT Apps SDK Development Guide ## Overview Create ChatGPT Apps with interactive widgets that render rich UI inside ChatGPT conversations. Apps combine MCP servers (providing tools) with embedded HTML widgets that communicate via the `window.openai` API. --- ## window.openai API Reference Widgets communicate with ChatGPT through these APIs: ### sendFollowUpMessage (Recommended for Actions) Send a follow-up prompt to ChatGPT on behalf of the user: ```javascript // Trigger a follow-up conversation if (window.openai?.sendFollowUpMessage) { await window.openai.sendFollowUpMessage({ prompt: 'Summarize this chapter for me' }); } ``` **Use for**: Action buttons that suggest next steps (summarize, explain, etc.) ### toolOutput Send structured data back from widget interactions: ```javascript // Send data back to ChatGPT if (window.openai?.toolOutput) { window.openai.toolOutput({ action: 'chapter_selected', chapter: 1, title: 'Introduction' }); } ``` **Use for**: Selections, form submissions, user choices that feed into tool responses. ### callTool Call another MCP tool from within a widget: ```javascript // Call a tool directly if (window.openai?.callTool) { await window.openai.callTo
- Overview
- window.openai API Reference
- sendFollowUpMessage (Recommended for Actions)
- toolOutput
- callTool
- Critical: Button Interactivity Limitations
- What Works
- What May Not Work
- Recommended Pattern: Suggestion Buttons
- Architecture Summary
- Quick Start
- Widget HTML Requirements
- Basic Widget Template
- Key Widget Rules
cd my_chatgpt_app python main.py Server runs on http://localhost:8001 ngrok http 8001 Get URL like: https://abc123.ngrok-free.app
What does the building-chatgpt-apps skill do?
Guides creation of ChatGPT Apps with interactive widgets using OpenAI Apps SDK and MCP servers. Use when building ChatGPT custom apps with visual UI components, embedded widgets, or rich interactive experiences. Covers widget architecture, MCP server setup with FastMCP, response metadata, and Developer Mode configuration. NOT when building standard MCP servers without widgets (use building-mcp-servers skill instead).
How do I install it?
Run `npx skills add majiayu000/claude-skill-registry --skill building-chatgpt-apps-abdullahmalik17-digital-fte-2 --agent claude-code` — it drops the skill into your project so the agent can pick it up. Swap the --agent value for codex, cursor or copilot if you use one of those.
Where does this skill come from?
From majiayu000/claude-skill-registry, a repository with 534 stars. We read it straight from the repository tree rather than a submitted listing, so what you see here is what is actually published.
Is a popular skill a good skill?
Not necessarily. Stars measure attention, not adoption — a repository can trend for a week and be abandoned. That is why we show the weekly change from our own snapshots next to the total, instead of a single flattering number.