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Connect a host / Connect ChatGPT

Connect ChatGPT

Add the person's MCP URL to ChatGPT as a custom MCP server with no authentication.

ChatGPT calls the URL from OpenAI's servers, and Relay forwards each call to the app on the person's device. The person needs ChatGPT on the web, on a plan and workspace that allow custom MCP servers.

Add the server#

  1. Open ChatGPT Plugins, select the plus button, then Add custom MCP server.
  2. Enter a name, such as your app's name, and a description if you like.
  3. Under Connection, paste the MCP URL as the Server URL.
  4. Choose No authentication.
  5. Read the risk warning, select I understand and want to continue, then Create as a plugin.
  6. Install the plugin. In a chat, type @ and pick it to use its tools.
NoteChatGPT's menus change often. If a label differs, look for adding a custom MCP server in ChatGPT's settings: the Server URL and No authentication are what matter. Show these steps in your app next to the copy button.

Write tools ask for confirmation#

ChatGPT treats every tool without readOnlyHint: true as a write action and asks the person to confirm each call. Mark the tools that only read, in the annotations of your `hello`; Relay passes annotations through unchanged.

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tool

{  "name": "search_notes",  "description": "Full-text search of the person's notes",  "inputSchema": {    "type": "object",    "properties": {      "query": {        "type": "string"      }    },    "required": [      "query"    ]  },  "annotations": {    "readOnlyHint": true  }}

Setup works while the app is closed#

When the server is added, ChatGPT lists its tools. Relay answers from the tool list the app registered when it last connected, so the person can add the server while the app is closed, as long as the app has connected once. Calls made while the app is closed answer that it is not running, and cost nothing.

After you change your tools#

ChatGPT keeps the tool list it fetched. After an update that adds or changes tools and the app has reconnected, the person refreshes the plugin from its details page in ChatGPT's settings to pull the new list.

After a URL rotation#

A rotated URL makes the old one answer 404 at once. The person removes the server from ChatGPT and adds it again with the new URL.

Good to know#

  • ChatGPT does not publish its time limit for a tool call. Keep tools fast and answer within seconds where you can.
  • In a workspace, admins decide whether members may add custom MCP servers.