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ChatGPT

ChatGPT connects to MCP servers as remote connectors through Developer Mode, a beta feature in the desktop and web apps. Unlike Claude Desktop and the IDEs, ChatGPT does not run local stdio MCP servers — so you connect to the hosted endpoint over the network, and there is no local-server option here.

Enable Developer Mode

Section titled “Enable Developer Mode”

Custom MCP connectors live behind Developer Mode, a beta that may not be available on every plan. Turn it on in ChatGPT’s settings — its exact location varies by release, so look under Settings → Connectors (or Settings → Apps & Connectors) for the Developer Mode toggle.

Add the connector

Section titled “Add the connector”
  1. In Settings → Connectors, choose Create (the +) to add a custom connector.
  2. Set the server URL to https://mcp.oceanum.io/datamesh.
  3. Pick an authentication method (see below) and save.
  4. Wait for ChatGPT to scan the server and list the Datamesh tools.

Authentication

Section titled “Authentication”

ChatGPT’s connector dialog offers OAuth, no authentication, or — in some releases — an API-key / bearer token. There is no field for an arbitrary custom header, so the X-DATAMESH-TOKEN header used by the other clients is not an option here.

  • OAuth is not yet available for ChatGPT. The hosted sign-in flow does not currently work for ChatGPT’s OAuth flow.
  • If your connector offers a token or API-key field, enter your Datamesh token: the hosted server accepts a Datamesh token as a bearer credential. This is the quickest route where the ChatGPT UI exposes it.

Large data

Section titled “Large data”

The hosted server returns query_data results inline (capped ~50 MB), so large results can’t come back in the chat. Once connected, ChatGPT can call export_query, which on the hosted server returns a time-limited download link to the full result (fetch it out-of-band — the link needs no token, so treat it as a secret). ChatGPT cannot run the local server, so the direct export_query-to-file path isn’t available — for that, use Claude or an IDE.

Keep your token safe

Section titled “Keep your token safe”

Your Datamesh token grants access to all of your organisation’s permissioned datasources — including the ability to modify or delete them. Treat it as a secret, never paste it into a shared chat, and prefer the hosted read-only server for exploratory use.