ChatGPT is the one client of the four where custom MCP servers are gated behind a setting you have to find first. Connectors you create live under Advanced Settings, and Developer Mode has to be on in two places: once in settings to create the connector at all, and again in each conversation where you want to use it. This trips people up more often than anything else about the setup, so it is worth knowing before you start rather than after the connector appears to do nothing.
Once it is on, the connector works across every ChatGPT platform, Desktop, Mobile, and Web, because the connector list lives with your account rather than the app.
Warplet is a macOS app that connects hosted AI clients to MCP servers running locally on your Mac. If you have not set it up yet, start with How to use Warplet.
Before you start
Make sure Warplet is running and connected. The app lists one URL per MCP server under Use these URLs to connect your favorite LLM. Each URL routes to a specific MCP server: the DEVONthink URL routes to the DEVONthink MCP server, the Beeper URL to the Beeper MCP server, and so on. Copy the URL for the server you want to connect.
Add the connector
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Navigate to your ChatGPT connector settings page: https://chatgpt.com/#settings/Connectors.
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Click Advanced Settings.
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Toggle Developer Mode in https://chatgpt.com/#settings/Connectors/Advanced.
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Click Create to create a new MCP server.
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A form will appear. Fill it out with the following details:
- Name:
Warplet(or the name of the app you're exposing) - Server URL: your Warplet MCP URL, copied from the app
- Authentication:
OAuth - Toggle: I trust this application
- Name:
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Click Create to save the new MCP server connection.
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ChatGPT will take you through the authorization flow. When the Warplet authorization page appears, paste the bearer token shown in the Warplet app and approve.
Once connected, enable Developer Mode in a new chat to use your connector. You can then ask ChatGPT to use your local tools directly in the conversation.
Why the authentication field says OAuth
Warplet implements the OAuth 2.1 flow that MCP clients expect, so choosing OAuth is correct even though nothing about the setup feels like signing in to a service. ChatGPT fetches the discovery metadata from your tunnel, registers itself as a client, and redirects you to a Warplet-hosted authorization page. That page is what asks for the bearer token.
The token you paste there is what Warplet checks on every request afterwards. Nothing else about your Mac is exposed by it: the tunnel URL is public, and this token is the only thing standing between it and your local servers.
Troubleshooting
Your connector is not offered in a conversation. Developer Mode is per-chat as well as per-account. Turn it on in the chat you are actually working in, then ask again.
The connector fails to create, or the URL is rejected. Warplet needs to be running with a live tunnel when ChatGPT first fetches the URL, because it reads the discovery metadata during creation. Open the app, confirm it shows as connected, and try again.
You get a 401 after it was working. A 401 from Warplet means the bearer token did not match. Regenerating the token in the Warplet app invalidates any connector that authorized with the old one. Reauthorize the connector and paste the current token.
ChatGPT calls a tool that no longer exists. ChatGPT caches the tool list from when the connector was authorized. If you changed which servers Warplet exposes, or the local app gained or lost tools, remove and re-add the connector to force it to refetch.
Everything looks connected but every call fails. Check that the local MCP server itself is running. Warplet forwards to localhost and cannot launch the app for you.
Now connect an actual app
The connector above gives ChatGPT a path to your Mac. What it can do once it is there depends on which local MCP server that URL points at:
- Use DEVONthink with Claude, ChatGPT, Perplexity, and Grok
- Use Obsidian with Claude, ChatGPT, Perplexity, and Grok
You can add as many connectors as you have servers. Each Warplet URL is added separately.