building-chatgpt-apps SKILL.md skillF
building-chatgpt-apps from mjunaidca/mjs-agent-skills is an agent skill: a SKILL.md folder an AI agent loads when a task calls for it.
mdr add mjunaidca/mjs-agent-skills/building-chatgpt-apps@git:20251222.ace8bd5Pins git:20251222.ace8bd5 in mdr.lock. Pin the fingerprint instead.
- Audit grade
- F, 15 of 17 checks passed
- Kind
- SKILL.md skill
- Repository
- mjunaidca/mjs-agent-skills
- Path
.claude/skills/building-chatgpt-apps/SKILL.md- Versions recorded
- 1
- Latest version
- git:20251222.ace8bd5, committed Dec 22, 2025
- Size
- 13,522 bytes
- Repository stars
- 28
- License
- none declared
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).
Collected from public GitHub. Every version is saved exactly as it was and never changes. Install it at an exact version with the mdr tool, and every file is checked before it reaches your agent. The main file is checked against the SHA-256 fingerprint recorded here, and the others against the fingerprints GitHub keeps for its source commit. The automatic checks below grade the latest version, and the same checks always give the same file the same grade.
What the file says
# 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
…Read the whole file at its exact version.
How to install
mdr add mjunaidca/mjs-agent-skills/building-chatgpt-apps@sha256:b8aff5d8b7f84116The line at the top of this page pins the label git:20251222.ace8bd5, which is what most people want. This one pins the sha256 fingerprint of the contents instead, so it survives a label being moved. Either way the exact version is written to mdr.lock, and mdr install downloads and checks those contents again, so it installs them exactly or stops with an error.
[](https://markdownregistry.com/a/art_kye2glkva3smqx5p)
3 badge image fetches in 30 days. What the badge shows.
Versions
The registry has recorded 1 version of this file, committed on Dec 22, 2025.
Audit of the latest version
- FAIL, critical: No link to an exfiltration or paste host (matched: https://your-tunnel.ngrok-free.app)
- fail: No script tag (matched: <script)
- pass: Frontmatter block present
- pass: Frontmatter declares a name
- pass: Frontmatter declares a description
- pass: Size between 200 bytes and 200 KB (13522 bytes)
- pass: No zero-width or bidi control characters
- pass: No instruction hidden inside an HTML comment
- pass: No credential-shaped string
- pass: No instruction to send local credentials anywhere
- pass: No text hidden with inline styles
- pass: No prompt-injection phrasing
- pass: No curl or wget piped into a shell
- pass: No recursive delete of root, home or parent
- pass: No instruction to read or print local credentials
- pass: No base64 blob over 200 characters
- pass: No link to a raw IP address
Starting a new one? Use a template for SKILL.md on mdpantry, which passes every one of these checks and says what to change in it.
Source
mjunaidca/mjs-agent-skills · 28 stars · license none declared · pushed 2026-08-12 · branch main
API
GET https://markdownregistry.com/api/v1/artifacts/art_kye2glkva3smqx5p GET https://markdownregistry.com/api/v1/resolve?ref=mjunaidca/mjs-agent-skills/building-chatgpt-apps GET https://markdownregistry.com/api/v1/blob/b8aff5d8b7f84116b765cc384a9585e171455d6e41861d8d24af11776695e0c2
Your AI assistant does the legwork. You hear about the deals worth your word. Hand yours the standing instructions at modelranch.com and it joins the network that reads files like this one.
Guides: the SKILL.md format and its required fields · what to check before you install a skill · how to pin a skill to an exact version · where to find agent skills · keeping a team on the same skills · which agent file does what.