A process_refund tool rejects refunds above a $500 policy limit. The agent currently retries the call three times, then tells the customer there was "a technical issue." What should the tool return in this case?

Answer: B — isError, marked not retryable, with an explanation the agent can relay to the customer

This is a business-rule violation: the request is valid but policy forbids it, and retrying won't change that. Marking it non-retryable with a customer-friendly explanation stops the retries and lets the agent tell the customer what the limit is and what can happen next (b). Calling it transient (a) causes more retries. A fake pending success (c) misleads the customer. A generic message (d) is what produced the 'technical issue' reply.