Connect an MCP server to Claude and ChatGPT

With the Model Context Protocol (MCP), an AI agent gets tools from outside: it can upload files, query data or, as with VORREN, publish a website. This guide explains what's behind it and shows the setup in the common agents.

What is an MCP server?

An MCP server is a service that offers tools to an agent. When it connects, the agent asks which tools exist and calls them during the conversation when it needs them. You can see which tool it uses.

There are two kinds:

• Local servers run on your computer, usually as a program the agent starts.
• Remote servers run on the internet and are connected through an address. VORREN is one of them (https://mcp.vorren.de/mcp).

Remote servers with your own data require you to sign in. The usual way is OAuth: when you connect, your browser opens, you sign in to the service and grant access. You never give the agent a password.

Claude Desktop

Custom connectors work on all plans; on the free plan you get one custom connector.

1. Open Customize > Connectors, choose + Add and Add custom connector.
2. Enter the server's name and address, click Continue, and for authentication choose Sign in now.
3. Sign in in your browser and grant access.
4. In the conversation, turn the server on via + and Connectors.

On Team and Enterprise, an owner first sets up the connector under Organization settings > Connectors. After that, each member connects on their own.

Claude Code

In the terminal, one command is enough. For VORREN:

claude mcp add --transport http vorren https://mcp.vorren.de/mcp

The first time you use it, your browser opens so you can sign in. Claude Code then works in a folder on your computer, so your project's files are on your machine too.

ChatGPT

In ChatGPT, custom MCP servers that are allowed to change things only work with Business, Enterprise and Edu. On Pro, ChatGPT can use custom servers read-only, which isn't enough to publish.

1. Open chatgpt.com/plugins in your browser, click the plus button and Add custom MCP server.
2. Enter a name and, under Connection, the address; choose OAuth as Authentication.
3. Read the risk warning, confirm it and choose Create as a plugin.
4. In a new conversation, type @ and pick the server. The first time, you sign in in your browser.

On Business, someone with an admin or owner role sets up the server and makes it available to the workspace.

Other agents

Many agents can connect remote MCP servers with OAuth, Codex CLI for example. Usually you're looking for a setting for an "MCP server over HTTP"; that's where you enter the address.

What to watch out for

• Only connect servers you trust. A server sees what your agent sends it.
• Don't put passwords or keys in the chat. Good servers don't ask for them. With VORREN, you enter secrets only in the dashboard.
• Check what the agent is allowed to do. With VORREN, it can build previews and go live when you agree. Connecting domains and deleting projects only works in the dashboard.

How to continue from there with a website is in the guide Build and publish a website with Claude.