RudTasks is a personal tool: only its owner can sign in, and anyone else's sign-in is refused and their Google access revoked at once.
When its owner connects Claude, RudTasks asks Google for their email address (to check it's the owner) and access to their Google Tasks. It uses that access only to carry out what Claude asks for: listing, adding, changing, moving and deleting tasks and task lists.
RudTasks has no database and stores nothing. The Google access it gets is encrypted and given to the connecting app (Claude) as its sign-in token; tasks pass through on each request and aren't kept, logged or shared with anyone else.
To disconnect, remove RudTasks under "Third-party apps & services" in your Google account.