Hermes is a private household assistant. It is not a public product, and it is not offered to other Google accounts.
The person who operates it uses their own Google account so Hermes can help with ordinary household admin: reading and sending mail they ask it to handle, checking and updating the family calendar, and opening or editing Drive files, Docs, and Sheets they point it at. Contacts are read only, and only when a name or address is needed for one of those tasks.
Hermes does not sell Google data, does not show ads, and does not share that data with other companies. Access stays on the operator's private computer until they revoke it.
How that data is used, stored, and revoked is in the privacy policy.
Questions: magiclarsen@gmail.com