If you want to plug your own tools in via the Model Context Protocol, you know the question: how do I actually attach my MCP server to the big chat interfaces? Simon Willison — one of the most reliable practitioners in this space — just published a small but very concrete guide on exactly that. The direct comparison between Claude and ChatGPT is the most telling part.
On Claude: refreshingly simple
In Claude.ai it’s a straight line. You start from the + menu next to the prompt and click through to the «Add custom connector» modal. There you enter the MCP URL and — if needed — configure authentication. After that you can simply toggle the new connector on and off in the Connectors menu. Done.
On ChatGPT: the detour through Developer Mode
ChatGPT makes it noticeably more involved. First you have to enable Developer Mode for your account in the «Security and login» panel. Only then does the «New Plugin» modal appear — and yes, an MCP is simply called a «Plugin» in the ChatGPT UI. If your server doesn’t need OAuth, you set authentication to «No Auth».
On the web you then click the + next to the chat, type the name of the MCP to search for it, and select it. The first time, you’re prompted to enable the MCP before you can use it in a prompt.
A practical example
Willison wires in an unauthenticated MCP for his own blog: datasette.simonwillison.net/-/mcp. It’s built on datasette-mcp and lets you run read-only SQL queries against a copy of his site’s database. A nice example of how low-friction this kind of setup can be when there’s no authentication in the way.
My take
What I like about this small guide: it makes visible how differently the two platforms handle the same standard. MCP is designed to be open and cross-vendor — but the convenience of setting it up differs noticeably. Claude treats connectors as a normal part of the product. ChatGPT hides the same feature behind a developer mode.
For anyone experimenting with their own MCP servers — and there are more of us every week — this is a practical reference to follow along with. Exactly the kind of knowledge you look up once and then reach for again and again.
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