Download the Service Account Key
This one file lets the setup tool sign in to your project. It is the only credential the tool needs.
Open Project settings#
In the left menu, click Settings, then General.
Service accounts#
Open the Service accounts tab at the top of Project settings. Under Firebase Admin SDK, make sure Node.js is selected, then click Generate new private key and confirm with Generate key.
Note where it saved#
A file named like your-food-a1b2c-firebase-adminsdk-xxxxx.json downloads. You choose it in the setup tool next.
Treat this file like a password
It gives full control of your Firebase project. Never send it by email, never upload it to a website and never put it in Git. The setup tool reads it on your computer only: it copies the key to a temporary folder while a deploy runs and deletes that copy afterwards. You can delete the downloaded file after setup, and revoke old keys on the same Service accounts page.
The key cannot deploy everything on its own
A key from Firebase may deploy rules and data, but not indexes or Cloud Functions. That is normal: in the setup tool you click Sign in with Google once with the project owner's account and those parts deploy with your account. The next page shows how.
Done
You have the key. Now run the setup tool.