Phone bookings don't work first time, always secon...
# ❓・bug-reportn
Nikita
12/16/2025, 10:30 PMHi, I have an issue. When retell is sending a request to cal.com. The first request seems always to be in this format:
tool_call_id: bd0c0ea970da79ca
{
"time": "2025-12-17T16:00:00",
"timezone": "Europe/Brussels",
"name": "Julie Peeters",
"email": "hello@moon-landing.agency",
"execution_message": "Dank u wel, mevrouw Peeters. Ik leg uw afspraak nu vast voor woensdag 17 december om 16:00 uur voor een tandartscontrole."
}
Eventhough I asked clearly to add phone number. It does not send the phone number in the request.
When the AI receptionist aks again for the phone number. I get this request suddenly:
tool_call_id: 8dad00e9dda91c97
{
"time": "2025-12-17T16:00:00",
"timezone": "Europe/Brussels",
"name": "Julie Peeters",
"email": "hello@moon-landing.agency",
"attendeePhoneNumber": "+32488633600",
"title": "Tandartsafspraak",
"notes": "Eerstvolgende afspraak voor tandartscontrole",
"guests": null,
"rescheduleReason": null,
"execution_message": "Dank u wel, mevrouw Peeters. Ik verwerk nu uw afspraak voor woensdag 17 december om 16:00 uur. U ontvangt zo meteen een bevestiging per sms."
}
In the second request, it adds the phone number and other fields as well. I tried to prompt it better but it won't add the phone number in the fist requrest. I tried it 10 times with different prompts but still nothing.
How can this issue be resolved?
Could it be that retell ai always sent the first request where just the email is sufficient?
Nikita
12/16/2025, 10:33 PMI just got this answer from Cal.com support team
-----
The issue is that Retell needs to include the attendeePhoneNumber parameter in the first request for SMS functionality to work properly.
Since your event type is configured to collect phone numbers as a booking question (evidenced by the second request working with attendeePhoneNumber), you need to ensure Retell's integration sends this parameter from the start.
For SMS to work, we use Twilio integration which requires the phone number to be present in the initial booking request.
Check with Retell's support to modify their integration so it includes attendeePhoneNumber in the first API call, not just when prompted again. The parameter format should be: "attendeePhoneNumber": "+32488633682" (as shown in your working second request).
Without the phone number in the first request, our SMS system can't send the confirmation message immediately after booking.
Nikita
12/16/2025, 10:57 PMagent ID: agent_386f22c67ca05711777b21a32a
Nikita
12/21/2025, 2:03 PMAny news?
o
Omar Ashraf | Community Lead
12/22/2025, 3:18 PMHello @Nikita , can you send a call id that have this issue ?
n
Nikita
01/01/2026, 11:28 PM@Omar Ashraf | Community Lead tool_call_id: 8dad00e9dda91c97
o
Omar Ashraf | Community Lead
01/02/2026, 1:27 PMHello @Nikita , I need the call id it self so i can check it
n
Nikita
01/02/2026, 4:54 PM@Omar Ashraf | Community Lead
I tested it out on chat (not the chat bot but literally the chat functionality of the call for testing purposes). It don't seem to have a call ID. I also can not get the chat back it seems..
o
Omar Ashraf | Community Lead
01/02/2026, 5:14 PMI need a call id to be able to check it , can you reproduce it with a web call or phone call.