ChatGPT reaches Heldrey over the internet. A server that runs only on your machine will not connect.
OpenAI’s developer-mode pages (read 15 September 2026) do not describe plan scope in the same way. The developer guide lists Pro, Plus, Business, Enterprise, and Education accounts on the web and describes full access to read and write tools. The Help Center says full MCP, including write actions, is currently available to Business and Enterprise/Edu; Pro connections are limited to read and fetch. It does not explain Plus in that plan-specific section.
On Business, only admins and owners can enable and use developer mode. On Enterprise/Edu, admins grant access under Permissions & Roles → Connected Data; enabled members then turn it on under Settings → Apps → Advanced Settings.
OpenAI warns that developer mode includes write actions and that you should watch for prompt injection. Heldrey’s confirmations and its handling of calendar text as data are the server’s half of that caution.
The allow page is the same Heldrey page described under Claude and permissions.