Tool Result tool_call_id: 2e2c8deb51f15fd9 {"error":"Error calling Cal Booking API: Axios Error: error code: ERR_BAD_REQUEST, error message: Request failed with status code 400\nresponse status: 400\nresponse data: [{\"status\":\"1\",\"timestamp\":\"2\",\"path\":\"3\",\"error\":\"4\"},\"error\",\"2026-03-05T21:50:16.235Z\",\"/v2/bookings\",{\"code\":\"5\",\"message\":\"6\",\"details\":\"7\"},\"BadRequestException\",\"attendee property is wrong, attendee email or phone property is wrong,Attendee must have at least one contact method (email or phone number) \",{\"message\":\"6\",\"error\":\"8\",\"statusCode\":400},\"Bad Request\"]"} https://cdn.discordapp.com/attachments/1479235447208280186/1479235447573053595/stjysthtsrhtg.png?ex=69ab4cdd&is=69a9fb5d&hm=848b83e2fe5034044a962fbd07e3d8a769a2e7388f000c8900befbf36e875ce1& https://cdn.discordapp.com/attachments/1479235447208280186/1479235448005070939/image.png?ex=69ab4cdd&is=69a9fb5d&hm=3d277b44faf2796395a3103ec37fa897630bd5b90ad34d3d43300a2dc429fc4a& https://cdn.discordapp.com/attachments/1479235447208280186/1479235448453988464/image.png?ex=69ab4cdd&is=69a9fb5d&hm=a89ae45f6b6483e66de2612d138fb18c7f231b83507781ac669345fda55d5a81&

Hi @Freysinn13

hi

400 Bad Request error indicates: Attendee must have at least one contact method email or phone number. Does your agent's prompt instructs to collect number or email

my system prompt collects phone number but not email, i wanted to not use it because receptioniat are bad at taking correct email

can you share your agent id and a call id

Yess ok

OK i send this to internal team to look

ok thanks

Hi @Freysinn13 The 400 error comes directly from Cal.com: “Attendee must have at least one contact method (email or phone number)”. Even though your prompt collects a phone number only, Cal.com still expects that phone to be passed into the attendee object. Please confirm: There is no Cal.com setting requiring an email specifically.

What’s likely happening Your AI does this: Agent asks for phone number ✔️ User says phone number ✔️ But the function/tool payload sent to Cal.com does not include the phone field ❌ So Cal.com rejects it with 400 Bad Request. YES chatgpt explained this to me, why is it not working?

Hello @Freysinn13 , this is purely a field mapping issue on your integration layer between Retell and Cal.com. The schema you defined collects phoneNumber, but you need to ensure it’s actually passed to Cal.com's API using the expected field name (phone inside attendee). Your Retell tool schema collects: { "phoneNumber": "+3541234567" }But Cal.com expects: { "attendee": { "phone": "+3541234567" } }

im talking to chatgpt and cal.com now and yes there are other issues too