An agent that only ever needs to read product data and write to a specific spreadsheet shouldn't have write access to the full database, even if it's "never going to use it that way" — prompts are guidance, not a security boundary.
Most agent tasks need far more read access than write access. Granting broad read but narrow, explicit write permissions limits the blast radius of a mistake to the specific things the agent is actually supposed to change.
Anything that can't be easily undone — sending an email, charging a card, deleting data — goes through a human confirmation step regardless of how confident the agent is. This is the one rule we don't make exceptions to.