GY Tools is a set of small, single-user software utilities written and operated by their owner for personal use. Nothing here is offered to the public as a product or service, and no accounts can be created.
The current utility, Mail Capture, is a desktop program that runs on its owner's own computer. With the owner's explicit authorization it reads email messages from the owner's own Gmail mailbox that carry a specific label, stores a copy of those messages locally on that computer, and records structured data derived from them for the owner's personal record-keeping. It uses read-only access; it does not send, modify, or delete email.
Only the owner. The software is not distributed, and the OAuth application associated with it is authorized solely against the owner's own Google Account.
Read the Privacy Policy for a plain statement of how Google user data is accessed, used, stored, and shared (it is not shared).