ChatGPT MCP Not Working: Fixes That Match the Product
If ChatGPT MCP is “not working,” it is usually Developer mode off, a free plan, a workspace policy, a localhost URL, or the app not enabled in that chat. Custom MCP in ChatGPT is a Developer mode app you attach per conversation. Saving it in settings does not turn it on everywhere.
Google already suggests chatgpt mcp not working and a full set around chatgpt developer mode mcp (access, local MCP, without developer mode). This page is the repair list. “Can it even use MCP?” is Can ChatGPT use MCP tools?. Official setup: OpenAI Developer mode and Connect ChatGPT.
Check these in order
| What you see | Likely cause | Fix |
|---|---|---|
| No Create / plus button on Plugins or Connectors | Developer mode off, or free plan | Plus, Pro, Business, Enterprise, or Education. Settings → Apps → Advanced settings → Developer mode. OpenAI has moved this toggle; if it is missing, look under Security / workspace policy. |
| Create exists, connection fails | URL is http://, localhost, or missing /mcp | Public HTTPS. ToolRouter: https://api.toolrouter.com/mcp. |
| Connected in settings, never used in chat | App not attached to *this* conversation | New chat → + → enable the ToolRouter app / Developer mode sources. |
| Tools listed, model never calls them | Prompt is vague, or built-in tools win | Name the app: “Use ToolRouter to audit this URL.” |
| Works for you, not for the team | Workspace admin has not allowed Developer mode | Owner enables it. Business/Enterprise can lock it. |
| “Always allow” kicks you into OAuth again | Known Developer mode footgun in some builds | Approve once for the session. File a host bug if it repeats. |
OpenAI’s current Developer mode doc (checked 31 August 2026) lists Pro, Plus, Business, Enterprise, and Education on the web. It is not the free plan. SSE and streaming HTTP are the supported transports. Local stdio npx is a Cursor/Claude Code pattern, not ChatGPT’s.
Community threads on the OpenAI forum show the same pattern: settings say connected, the chat toggle does not list the custom app. When that happens, it is a host regression or a workspace policy, not your URL. Confirm the URL in MCP Inspector, then wait for OpenAI or switch to Claude/Cursor for the same catalog.
A working ToolRouter setup
- Turn on Developer mode.
- Create an app: name
ToolRouter, URLhttps://api.toolrouter.com/mcp. - Every new chat: enable that app from +.
- Prompt with a job, not a protocol: “Audit https://example.com for SEO.”
No API key in the URL. Account auto-provisions. Same catalog as Claude and Cursor. How to add MCP to Cursor if you needed local npx instead.
Team: one ToolRouter team so people are not each debugging a different URL. For teams. Manage MCP for a team.
Give your AI superpowers. Copy one instruction and paste it into your AI.
Localhost will not work
ChatGPT talks to a public HTTPS server from OpenAI’s side. http://127.0.0.1:3000/mcp is your laptop. Use a tunnel only for a server you are building. For a product catalog, use the hosted URL.
That is the #1 “I followed a Cursor tutorial in ChatGPT” failure.
When the host is the problem
If Inspector can list tools from https://api.toolrouter.com/mcp and ChatGPT still will not call them after you attached the app, you have a ChatGPT bug or policy. Keep using Claude or Cursor against the same catalog until the chat client catches up. Do not rebuild the server for a UI toggle.
Connect ToolRouter, attach the app in the chat, and ask for the job.
Frequently Asked Questions
Can I use MCP in ChatGPT without Developer mode?
**Not for a custom server.** Directory/listed apps can connect without it. ToolRouter today is the custom Developer mode app path.
Why did it work last week?
**Menus moved (Connectors → Apps/Plugins) and OpenAI has shipped regressions on custom apps.** Re-enable Developer mode, Refresh the app, start a **new** chat, attach it again.
Does the team share one Developer mode toggle?
**Workspace admins can hide it.** If your toggle is missing at work, it is policy, not your account being “too junior.”
