Connecting ChatGPT to the NIS2 walkthrough

How do I add the walkthrough to ChatGPT?

MCP (Model Context Protocol) is the open standard an AI assistant uses to work with other software. The NIS 2 walkthrough offers an MCP server for it, and ChatGPT adds it as a custom server.

According to OpenAI, you open the Plugins page in ChatGPT, select the plus button, then "Add custom MCP server". Enter a name, for example nisd2, and under "Connection" the address below.

Then configure authentication, review the risk warning, confirm with "I understand and want to continue" and select "Create as a plugin". The labels are those in OpenAI's English documentation; your interface may word them differently.

Before that, an admin has to turn on "Allow AI assistants for this company" in the walkthrough's Settings. Your own account needs access to the walkthrough.

https://nisd2.eu/api/mcp

Signing in through the browser instead of a key

OpenAI states that ChatGPT cannot present custom API keys. The key you get in the walkthrough with "Create key" is therefore of no use in ChatGPT. You sign in through the browser instead, using OAuth: you allow access without giving ChatGPT your password.

In doing so, ChatGPT registers itself with the walkthrough's sign-in service. According to OpenAI, ChatGPT can use a Client ID Metadata Document or automatic registration (Dynamic Client Registration) for this. The walkthrough offers only automatic registration; if you are asked, choose that.

After you sign in, nisd2.eu shows which assistant is asking for which company and where the browser returns to afterwards. The return addresses OpenAI lists are on chatgpt.com. If the page shows anything else, click "Decline".

With "Allow", ChatGPT receives a token, a kind of pass with an expiry date. It lasts an hour and can be renewed, at most until 90 days after you allowed it. Then you allow ChatGPT again.

Does the server have to be reachable from the internet?

Yes, or through a tunnel. According to OpenAI the server needs a public https address or the Secure MCP Tunnel, because the requests come from OpenAI's network. nisd2.eu is reachable from the internet, so you need no tunnel there.

For a self-hosted instance inside the company network, OpenAI describes the tunnel like this: a small program called tunnel-client runs in your network and opens the connection outwards. It passes the requests on to the server.

Setting it up takes tunnel permissions in your OpenAI account. We have not tested the tunnel with the walkthrough.

Without a tunnel, software on your own computer, such as Claude Code, reaches an instance inside the company network directly.

What ChatGPT fills in, and what you confirm

ChatGPT reads the walkthrough and fills in what its items ask for, as you and with your rights. According to OpenAI, ChatGPT asks for your confirmation before write actions by default. The tool that fills in, fill_walkthrough_item, is marked as one that writes.

Before you confirm, read what ChatGPT is about to send: which item, which rows, which answers. A new answer replaces what the field held. According to OpenAI you can have ChatGPT remember your approval for a tool until the end of the conversation; it then stops asking in that conversation.

Upload evidence in the app. For a file, an assistant has to send its contents to storage itself; we have not tested whether ChatGPT can do that.

ChatGPT cannot finish, decide or sign anything, because the server has no tool for it. That stays with you, in the app.