By skyforbes 
Want to make ChatGPT more than a chat window — an app platform? The new Apps SDK lets you build web-backed apps that run inside ChatGPT conversations: tools the model can call, and rich UI components the model can render inline. This article walks you through a small, real project from zero → running locally → testing inside ChatGPT Developer Mode. I’ll keep it concrete with code, tips, and the exact commands you’ll copy-paste.
(Short version: you’ll build a tiny “Pizza Finder” MCP server that advertises a search_pizzas tool, returns structured results, and surfaces a little interactive component in the chat. Then you’ll test it via ngrok in ChatGPT Dev Mode.)
Sources that explain the platform, the open Model Context Protocol (MCP) and the example repo I used while writing this: OpenAI’s Apps announcement and docs, the Apps SDK reference, and the official examples gallery. OpenAI Developers+4OpenAI+4OpenAI Developers+4
Why this is cool (and different)
- ChatGPT can call your tools (like APIs) during a conversation and then show the result inline.
- You can return structured data so the assistant reasons about it, plus
_metaHTML that the Apps SDK renders as a tiny UI widget (tables…