Pick Docs, Sheets and PDFs in Google's own picker. OneType reads only those files, keeps them in sync and cites them in its answers.
In short
Your documents
Pick documents in Google's picker and your agent learns from them, next to your website, files and Q&A.
Nothing else in your Drive is read.
The Google Docs, Sheets and PDFs you pick.
Re-read on your plan's schedule, or with Sync now.
Decide if visitors may open the document.
Answers
When an answer comes from a Drive document, it carries a numbered source, so visitors can see where it came from.
A source after every fact.
If your documents don't cover it, it says so.
Only the files you pick are read.
Setup
No code: sign in with Google and pick your files.
In your agent, open Knowledge, choose Add source and Google Drive, and sign in with Google.
Choose the files your agent should know.
Test the answers in the preview, then make the agent live.
Create your agent, then add Google Drive as a source in its Knowledge tab.
Google Drive is a trademark of its owner.