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:

// Trigger a follow-up conversation
if (window.openai?.sendFollowUpMessage) {