Unable to create recurring webinar: Request Body should be a valid JSON object

API and Webhooks
1

I am getting a Request Body should be a valid JSON object error when attempting to create a recurring webinar but unfortunately this message is too vague and doesn’t help me figure out what’s wrong with the JSON I am submitting.

REQUEST:
POST https://api.zoom.us/v2/users/8lzIwvZTSOqjndWPbPqzuA/webinars
{
    "type": 9,
    "topic": "ZoomNet Integration Testing: recurring webinar",
    "agenda": "The agenda",
    "password": "p@ss!w0rd",
    "start_time": "2025-09-08T00:12:39Z",
    "duration": 30,
    "recurrence": {
        "type": 2,
        "weekly_days": [
            1,
            5
        ],
        "end_times": 2
    },
    "timezone": "UTC",
    "settings": {
        "approval_type": 1,
        "registration_type": 1,
        "audio": "telephony",
        "auto_recording": "local"
    },
    "tracking_fields": [
        {
            "field": "field1",
            "value": "value1"
        },
        {
            "field": "field2",
            "value": "value2"
        }
    ]
}

RESPONSE:
HTTP/1.1 400 Bad Request
Date: Fri, 08 Aug 2025 00:13:00 GMT
x-zm-trackingid: v=2.0;clid=us06;rid=WEB_3c76dbbfe6cf00095c34ba906cab3202
{
    "code":300,
    "message":"Request Body should be a valid JSON object."
}

After much trial and error I figured out the problem: the weekly_days property is expected to be a comma-separated string rather than an array of integer.

It so happens that about a month ago @elisa.zoom helped me with a problem when creating recurring events. Elisa pointed out that I was specifying weekly_days as a comma separated string but the API was expecting an array of integers.

The solution to the problem I am reporting today conflicts with the advice I received from @elisa.zoom in the previous case. If I understand the situation correctly, there are some scenarios (such as when creating recurring webinars) where weekly_days must be specified as a comma-separated string and there are other scenarios where weekly_days property must be specified as an array of integers (such as when creating a recurring event for example).