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ChatGPT connects to remote MCP servers through Developer mode. You create an app for OnlyX once, sign in with OAuth, and then turn it on in any chat. ChatGPT has no install link for MCP servers, so this takes about a minute of clicking. You need:
  • ChatGPT on the web with a Plus, Pro, Business, Enterprise or Edu plan (Developer mode is not available on Free). On Business, Enterprise and Edu, a workspace admin may first need to allow Developer mode or custom connectors for members.
  • To be an owner or admin of your OnlyX workspace, to approve the connection.
The server URL is:
1

Turn on Developer mode

In ChatGPT open Settings → Apps & Connectors → Advanced settings and switch on Developer mode. (In some ChatGPT versions the switch is under Settings → Security and login.) Business, Enterprise and Edu admins control this under the workspace’s permission settings.
2

Create the OnlyX app

Still in Settings → Apps & Connectors, click Create (in some versions Create app or +). Fill in:Leave client ID and secret empty: OnlyX registers ChatGPT automatically. Confirm that you trust the app and click Create.
3

Sign in to OnlyX

ChatGPT opens OnlyX’s sign-in page. Sign in, choose the workspace, optionally limit ChatGPT to some creators, review the permissions, and click Approve. You are sent back to ChatGPT, and OnlyX appears under your apps (new Developer mode apps are listed as drafts).
4

Use it in a chat

In a new chat, open the + menu (or Tools), choose Developer mode, and turn on OnlyX. Then ask: “Using OnlyX, which workspace am I connected to?”

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Confirmations

ChatGPT asks you to confirm every action that is not read-only, and shows what it is about to send. Read it: for send_message that is the exact text, media ids and priceCents that will reach the fan. OnlyX’s tools also tell ChatGPT to confirm fan-reaching actions with you in the chat first.

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API keys

ChatGPT connects with OAuth only; it cannot send a custom API key. To give ChatGPT less access, limit it to specific creators on the OnlyX consent screen, and revoke it any time in Settings → API & MCP → Connected apps. For read-only assistant access with a key, use a client that supports headers, such as Claude Code, Cursor or VS Code.

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Troubleshooting

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