building-chatgpt-apps
Guides creation of ChatGPT Apps with interactive widgets using the 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 --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.
# Apps SDK Development Guide ## Overview Create ChatGPT Apps with interactive widgets that render rich UI inside ChatGPT conversations. The Apps SDK combines MCP servers (providing tools) with embedded HTML widgets that communicate via the `window.openai` API. **Official Documentation**: https://developers.openai.com/apps-sdk/ **Examples Repository**: https://github.com/openai/openai-apps-sdk-examples ## Three-Layer Architecture ``` ┌─────────────────────────────────────────────────────────────────┐ │ ChatGPT UI │ │ ┌─────────────────────────────────────────────────────────────┐│ │ │ Widget (iframe) ││ │ │ React/Vanilla JS + CSS ││ │ │ window.openai.* APIs for host communication ││ │ └─────────────────────────────────────────────────────────────┘│ │ │ │ │ ▼ │ │ ChatGPT Backend │ │ │ │ │ ▼ │ │ MCP Server (HTTP/SSE) │ │ - Tools: exposed actions │ │ - Resources: widget HTML (text/html+skybridge) │ │ - Response: structuredContent + _meta │ └─────────────────────────────────────────────────────────────────┘ ``` **Flow**: User prompt → Model invokes tool → Server returns structured data → Widget renders → Model narrates result --- ## window.openai API Reference Complete API surface for w
- Overview
- Three-Layer Architecture
- window.openai API Reference
- State & Data Access
- Runtime Actions
- Layout Control
- Context Properties (Read-Only)
- Code Examples
- Tool Definition with Metadata
- TypeScript/Node.js Pattern
- Python/FastMCP Pattern
- Tool Metadata Reference
- Response Payload Structure
- Widget Resource Registration
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 the 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 --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.