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Use ChatSyncs from Gemini CLI, Google’s AI agent for the terminal.

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Before you start

  • Gemini CLI installed and signed in. Run gemini --version. If it isn’t found, install it from geminicli.com.
  • A terminal. On a Mac, open the Terminal app (Applications → Utilities). On Windows, open PowerShell from the Start menu. In paths below, ~ means your home folder.
  • Your ChatSyncs API key, from the API Developer Console. How to find it.
This page connects Gemini CLI with your API key directly: one command and you’re done. If you’d rather not store the key in a file, ChatSyncs also supports Gemini CLI’s browser sign-in. See Can I sign in through the browser instead?.

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Connect

1

Open a terminal

Mac: the Terminal app. Windows: PowerShell. Check Gemini CLI is there by running gemini --version: it should print a version number.
2

Add ChatSyncs with your key

In a terminal, run this command, with YOUR_CHATSYNCS_API_KEY replaced by your key (keep the word Bearer and the space after it):
--scope user makes ChatSyncs available in every folder, not just the current one.
3

Check it's listed

Run gemini, then type /mcp and press Enter. chatsyncs is listed as connected, with its tools.

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Prefer editing the file?

The command above edits ~/.gemini/settings.json for you, which is the easiest way. If you’d rather edit the file yourself, the ChatSyncs part looks like this. If the file already has other settings, put "mcpServers" next to them inside the outer { }, separated by a comma:

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Check it worked

In Gemini CLI, ask:
“List my WhatsApp templates.”
Gemini asks you to confirm the ChatSyncs tool call, then lists your templates.

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Disconnect

Your key was stored in ~/.gemini/settings.json; removing the server deletes it from there. If the key may have been seen by anyone else, regenerate it.

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Frequently asked

It’s stored in plain text in settings.json (in the .gemini folder in your home folder), and the command you typed may be kept in your terminal’s list of past commands. That’s fine on your own computer. Don’t share or sync the file, and regenerate the key if you stop using Gemini CLI or the computer is shared.
Gemini CLI has a "trust": true setting that skips every confirmation for a server. Don’t use it with ChatSyncs: it would let Gemini send WhatsApp messages without asking.
Yes. Add ChatSyncs without the header:
Then run gemini, type /mcp auth chatsyncs and press Enter. The ChatSyncs page opens in your browser: paste your API key and click Authorize. Your key is then never written into settings.json. If the sign-in ever fails, use the header method above instead.

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Gotchas

  • “Missing issuer parameter in response.” ChatSyncs sends this detail since 5 October 2026. Run /mcp auth chatsyncs again. If it still appears, remove ChatSyncs and add it back with the --header command above.
  • Added it but it’s missing in another folder. You left out --scope user, so it was saved only for the folder you were in. Remove it with gemini mcp remove chatsyncs and add it again with --scope user.
  • Every action says the key is missing or invalid. Check the header reads exactly Authorization: Bearer followed by your key, with nothing else and no extra spaces.