Gemini takes custom apps, which is Google's name for a remote MCP server you add yourself. It wants the address and nothing else.
Add it
Open gemini.google.com/apps, which is the Connected apps page, and choose Add a custom app. Paste the address as the MCP server URL, press Next and allow it. You add it in the web app; once it is there it works in the Gemini app on your phone too.
https://makehybrid.com/mcp/<your key>
What Google asks of the account
Custom apps are offered on some Google accounts and not others — a personal account rather than a work or school one, English, and the web app rather than the phone, at the time of writing. If there is no Add a custom app on that page, that is the reason, and Google's own help page is the one to believe over this one. Gemini also asks you to confirm anything that writes, every time.
Check it
Ask it to list your connected LinkedIn accounts. Your accounts back means it worked.
Questions people ask
Does it want a local server?
No, and it will not take one. A command you run with npx or uvx is a local server; this is a remote one over HTTPS, which is what the Connected apps page expects.
Is there a sign-in step?
No. Your key is already inside the address, so there is no OAuth client to set up and no header to add.
Can I give it only part of this?
Yes. Every agent has an address of its own — /inbox/mcp/<key> is the shared inbox and nothing else, /asana/mcp/<key> is Asana — and a custom app is one address, so add the one you want it to have.