Connect Gemini

Gemini speaks MCP in two places. The Gemini app adds Hiasynth from its settings, no terminal involved, but Google only offers that to personal accounts in the United States for now. Everyone else, and anyone who lives in a terminal, uses Gemini CLI, which takes one command. Both are below.

The Gemini app

Google currently limits custom connected apps to people aged 18 or over, in the United States, on a personal Google account, with Keep Activity switched on, in English. If the menu below is missing, that is why. Skip down to Gemini CLI, which works everywhere, or use another assistant until Google widens it.

Add Hiasynth as a custom app

  • On a computer, open gemini.google.com and go to Settings, then Connected Apps.
  • Under Custom apps, click Add a custom app.
  • Paste the address below as the MCP server URL and click Next.
https://mcp.hiasynth.co

Say yes to the handshake

A Hiasynth page opens. Sign in with Google, GitHub or Discord, read what Gemini is asking for, and click Approve and subscribe, or Approve if you already have a subscription.

Ask

Custom apps are added on the web but work in the Gemini mobile app too. Ask:

Who lives within three kilometres of Södermalm in Stockholm, and what is the area like by day?

Gemini CLI

For people comfortable in a terminal. It works everywhere, including inside Gemini Code Assist's agent mode, which reads the same settings.

Add the server

Run this in your terminal:

gemini mcp add --transport http hiasynth https://mcp.hiasynth.co

Sign in

Start Gemini CLI, then type:

/mcp auth hiasynth

Your browser opens the Hiasynth page. Sign in with Google, GitHub or Discord (new here? that just made your account), read what is being asked, and approve. The card will note that the client runs on your own computer. That is exactly right.

Ask

Back in the terminal:

How many households in Bavaria have children under ten and an electric car, and where are they densest?

Gemini reaches for Hiasynth, runs the count, and answers from the numbers.

Prefer to edit the file yourself? It lives at ~/.gemini/settings.json, or .gemini/settings.json inside a project. Gemini CLI calls the address httpUrl, not url, which is the one thing that trips people up when copying a config from another client.

{
  "mcpServers": {
    "hiasynth": {
      "httpUrl": "https://mcp.hiasynth.co"
    }
  }
}

For a script or a machine with no browser, create an API key on your connector page and add "headers": "Authorization": "Bearer YOUR_API_KEY" next to httpUrl.

What next

  • What to ask: questions that show what Hiasynth is good at.
  • Pricing: one subscription, credits that meter what you ask.
  • Troubleshooting: the short list of things that go wrong, and the fix for each.