Hey everyone,
I’m getting a 422 Validation Failed error from the Cliniko API when creating an appointment via n8n HTTP Request.
Error returned:
{
“errors”: {
“max_attendees”: “is not a number”
},
“message”: “Validation Failed”
}
What I’m sending in the request:
max_attendees value resolves to 1
Expression used:
{{ $(‘Prepare data’).item.json.max_attendees }}
The resolved value shown in n8n preview is 1 (not null, not empty)
Context:
Other numeric fields in the same request work correctly
Removing max_attendees is NOT an option (Cliniko requires it in my case)
I’ve already confirmed the field exists and the value is present
This works in other requests, but Cliniko keeps rejecting this one
Question:
Does Cliniko require max_attendees to be explicitly cast as a number (e.g. Number()) or is there something specific about how their API validates this field?
If anyone has successfully created appointments with max_attendees via n8n, I’d really appreciate seeing the exact format you used.
Thanks 
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