A support agent pulls order data from an MCP tool that returns Unix timestamps and numeric status codes, and shipment data from another that returns ISO 8601 dates and text statuses. The agent sometimes miscalculates whether a return is within the 30-day window. What is the most effective fix?

Answer: D — Add a PostToolUse hook that converts every timestamp and status code to one format before the agent sees it

A PostToolUse hook intercepts tool results and normalizes heterogeneous formats before the model processes them, so every comparison is made on consistent data. A prompt table (a) and asking the model to convert (b) still rely on it interpreting each format correctly every time, and checking the final answer (c) catches errors only after the agent has reasoned over raw data.