Why My AI Agent Kept Lying About the Date

What you'll build

A fix for a problem every Vapi voice agent builder hits: the agent confidently tells callers the wrong date. Mine was a simple wine warehouse store assistant - asked "what day is it?", it answered "Tuesday, October 31st, 2073." Completely wrong, with full confidence. You'd think AI would know the date by now. It doesn't.

The fix is a tiny Make.com webhook that hands your agent the real date and weekday in real time, wired in as a Vapi tool. I dealt with this for a while before landing on this solution - it might not be the best, but it works. And the thing that cost me the most time turned out to be one letter.

What you'll need

• A Vapi account with a voice agent set up
• A Make.com account
• ~10 minutes

Step 1: Confirm the bug

Ask your agent what day it is. If you haven't given it a date source, it'll hallucinate one - a year like 2073, the wrong weekday, whatever. The LLM has no live clock; it needs a tool.

Step 2: Build the webhook in Make.com

Create a new Make.com scenario with two modules:

1. A Custom webhook
2. A Webhook response connected to it

The webhook response is just telling your Vapi voice agent what date it is and what weekday. It looks complicated - it's really not. Grab the exact response body from my doc (https://docs.google.com/document/d/1XUmJAGR3SVUttYKRMnjDSYi5_C8t-B30-WZdt-poLEE/edit?usp=sharing), or build your own with Make's date formatting.

The one letter: use uppercase D in the date format, not lowercase d. ChatGPT may tell you to use lowercase - that will not work, especially for the weekday portion. This is where I burned most of my time.

Step 3: Set the webhook to run automatically

Before leaving Make, set the scenario to "Immediately as data arrives." Otherwise you'd have to manually click run every time the voice agent tries to pull the date - this makes it fire on its own.

Step 4: Create the tool in Vapi

Copy the webhook URL from Make, then go to the Vapi dashboard → Tools and create a new tool:

• Name: get_date
• Description: "Retrieves the current date and weekday in real time (Eastern time) from Make, so the agent can accurately reference today's date during calls."
• URL: your Make webhook URL
• HTTP method: GET

Nothing else you really need. Attach the tool to your assistant.

Step 5: Test it

Call the agent and ask again. Mine: "It's Wednesday, October 22nd, 2025." Tool ran, correct date, correct weekday. That's it - pretty important fix for any voice agent doing bookings, hours, or anything time-aware.

Bonus tips from the video

• Get ahead of Twilio. If you're planning to run your own AI automation agency, submit the form for a number (toll-free or local) as soon as possible - regulations are tightening and campaigns are getting rejected, so there's paperwork either way. Start it early.
• Demoing? Use Vapi's phone numbers. Vapi has a phone number section where you can create a number quickly and attach it to a demo for showing potential clients. Just don't use it as an official business number.
• Wispr Flow. Instead of typing into ChatGPT, hit the Fn key and speak - way faster than typing. Simple productivity hack that adds up.

Good luck and happy building.

Resources

• Webhook response body doc - https://docs.google.com/document/d/1XUmJAGR3SVUttYKRMnjDSYi5_C8t-B30-WZdt-poLEE/edit?usp=sharing
• Vapi - https://vapi.ai
• Make.com - https://www.make.com
• Wispr Flow - the voice-to-text I use, 1 month free: https://wisprflow.ai/r?AUSTIN16480