When an AI agent makes a costly mistake, who is accountable?

AI agents are moving beyond simple chatbots. Some companies are beginning to use them for research, scheduling, customer support, reporting, and internal operations.
The interesting question is not whether an AI agent can complete a task. It is whether teams can trust it to make decisions, handle exceptions, and work without constant supervision.
My guess is that adoption will depend less on raw intelligence and more on accountability. When an AI agent makes a mistake, who is responsible: the employee, the manager, or the company that built the system?
Would you accept an AI agent as part of your team, or would you only trust it as a tool?