Just be aware that if you don't add a key (and set up billing) youre granting Google the right to train on your data. To have persons read them and decide how to use them for training.
> To help with quality and improve our products, human reviewers may read, annotate, and process your API input and output. Google takes steps to protect your privacy as part of this process. This includes disconnecting this data from your Google Account, API key, and Cloud project before reviewers see or annotate it. Do not submit sensitive, confidential, or personal information to the Unpaid Services.