ChatGPT Ask User MCP

A tiny remote MCP App for ChatGPT Web, deployed on Cloudflare Workers.

It gives ChatGPT one tool, ask_user, so the model can stop at a decision point, show you a native-looking question card, receive your choice, and continue the same conversation.

Use it

1. Deploy to Cloudflare

Click Deploy to Cloudflare above.

Cloudflare will clone the repository, build the widget, deploy the Worker, and give you a public workers.dev URL.

No database, KV, Durable Object, API key, or other Cloudflare resource is required.

After deployment, your MCP endpoint is:

https://<your-worker>.<your-subdomain>.workers.dev/mcp

Health check:

https://<your-worker>.<your-subdomain>.workers.dev/health

2. Add it to ChatGPT Web

1. Enable Developer mode in ChatGPT.

2. Open Settings → Apps → Create.

3. Enter the deployed URL ending in /mcp.

4. Select No authentication.

5. Choose Scan tools, then save/create the app.

6. Enable/select the app in a chat.

Test prompt:

Work through this task. Whenever a choice would materially change the approach, use Ask User to ask me instead of deciding for me.

Related MCP server: Clarify MCP Server

Behavior

ChatGPT is doing a task
        ↓
needs your decision
        ↓
calls ask_user
        ↓
┌──────────────────────────────┐
│ Which approach should I use? │
│ ○ Option A                   │
│ ○ Option B                   │
│                              │
│                    [Submit]  │
└──────────────────────────────┘
        ↓
you submit
        ↓
the widget sends your answer
as a follow-up message
        ↓
ChatGPT continues the task

The tool supports:

• single choice

• multiple choice

• optional free text

• free-text-only questions

• short context/explanation text

• custom submit button labels

ChatGPT-native appearance

The widget uses OpenAI's official @openai/apps-sdk-ui package together with MCP host styling via useHostStyles().

It inherits ChatGPT's typography and host theme variables, so light/dark mode follows ChatGPT automatically instead of using a separate hand-written theme.

Architecture

ChatGPT Web
    │
    │ Streamable HTTP MCP
    ▼
Cloudflare Worker
    │
    ├── ask_user tool
    │
    └── embedded self-contained widget HTML
             │
             ▼
        ChatGPT iframe
             │
             └── sendFollowUpMessage()
                     │
                     ▼
               same conversation

The Worker is stateless. There is no database and no conversation storage.

Scope

This repository is intentionally only for the ChatGPT Web remote MCP use case:

• one Cloudflare Worker

• one public /mcp endpoint

• one ask_user tool

• one interactive UI widget

• no database

• no user data storage

• no Docker

• no npm/CLI distribution

• no Render service

• no other MCP-client compatibility work

Local development

Requirements: Node.js 20+.

npm install
npm run build
npm run dev

Wrangler will start the Worker locally. ChatGPT Web still requires a public HTTPS endpoint, so local mode is mainly for development and MCP Inspector testing.

Deployment from the CLI

If you already use Wrangler:

npm install
npm run deploy

Implementation

• MCP server: @modelcontextprotocol/server

• Cloudflare MCP transport: createMcpHandler from agents/mcp/server

• MCP App binding: @modelcontextprotocol/ext-apps

• UI: React + official @openai/apps-sdk-ui

• Theme: MCP host styles / ChatGPT light-dark mode

• Continuation: ChatGPT sendFollowUpMessage(), with MCP Apps sendMessage() fallback

• Widget bundle: Vite + vite-plugin-singlefile

• Hosting: Cloudflare Workers

• Storage: none

License

Copyright (C) 2026 zjm54321

Licensed under the GNU General Public License v3.0 only (GPL-3.0-only). See LICENSE.