Hi everyone, I’m working on a Retell AI voice agent that integrates with Cal.com to check and book appointment availability. The Issue: When a user says something like: “Book an appointment tomorrow at 3 PM” The agent is not converting that into a full ISO timestamp like 2025-07-11 15:00. Instead, it’s sending "start_time": "tomorrow 3:00" to the check_availability function, which causes errors or broad time range behavior. I want it to: Parse “tomorrow 3 PM” into → 2025-07-11 15:00 And end_time as → 2025-07-11 15:30 Tools I'm Using: Retell AI (Voice Agent running GPT-4.1 mini) Cal.com for real-time booking availability Function call: check_availability My Current Prompt Logic: Ask for their preferred date and time. If the user specifies a time (e.g., "tomorrow at 1 PM"), convert it into a precise 30-minute slot. Call the function check_availability with: - start_time: the exact time requested in ISO format (e.g., 2025-07-11 13:00) - end_time: 30 minutes after the start_time Do NOT use the full-day time range unless no time is provided. What I Need Help With: How can I ensure the model always resolves phrases like “tomorrow” or “next Monday” into full ISO timestamps? Is there a better prompt or formatting method that works with Retell and GPT-4.1 mini? Has anyone already solved this with Retell + Cal.com? Any guidance, working examples, or fixes would be appreciated. Thanks, Sukumar