The extension tool and parameter names collided with something Gemini CLI rejected. Miro updated their tool and parameter names to fix it: restart Gemini CLI so it re-fetches the tool list from the extension, and chat works again. If the 400 persists, make sure you are on the latest version of the miro-ai extension.

Context: GitHub issue on miroapp/miro-ai: after installing the miro-ai extension, every Gemini CLI chat attempt fails with a 400 INVALID_ARGUMENT API error until the extension is removed.