ChatGPT Apps

A moonpeak project is a ChatGPT App. What moonpeak adds for ChatGPT, and how to try it.

ChatGPT Apps are MCP Apps. Every moonpeak resource carries both the MCP Apps metadata and the older ChatGPT Apps SDK keys, so ChatGPT renders your Views without extra work:

moonpeak	ChatGPT key
tool `resource`	`openai/outputTemplate`
tool `invoking`, `invoked`	`openai/toolInvocation/invoking`, `.../invoked`
tool `visibility: ["app"]`	`openai/visibility: "private"` and `openai/widgetAccessible: true`
resource `description`	`openai/widgetDescription`
resource `prefersBorder`	`openai/widgetPrefersBorder`
resource `csp`	`openai/widgetCSP`

ChatGPT-only hooks

import { useIsChatGPT, useWidgetState, useOpenAiGlobal, useUploadFile, useRequestModal, useUserAgent } from "moonpeak/chatgpt";

They read window.openai and do nothing outside ChatGPT. Prefer the portable hooks when one exists: useAppState already saves to ChatGPT's widget state.

Try it in ChatGPT

Deploy over HTTPS (see Deployment).
In ChatGPT: Settings → Apps → enable Developer mode → Create app.
Enter https://your-domain/mcp and save.
In a new chat, ask for something your tool handles.

The inspector's ChatGPT host replicates window.openai (globals, widget state, display modes), so most issues show up locally first.