Why is a .net core controller Post method not accepting the anti forgery token?

I’m trying to do a POST using an API call for a form using a reactive framework (Vue 3 in my case). I’m using .net 6.0. It is not accepting the anti forgery request token. I’m putting it in the body of the request like it is for a traditional form submit. The call in Javascript:

    var token = $('input[name="__RequestVerificationToken"]').val();
    var url = '/api/ShareAllocations';
    $.ajax({
        type: "POST",
        url: url,
        data: { fa: fa, '__RequestVerificationToken': token },
        success: function (result) {
            console.log(result)
        },
        complete: function (e) { },
        error: function (xhr, ajaxOptions, thrownError) {
            alert(xhr.responseText);
        }
    });

In Fiddler, the textView of the input looks like this:

Fa= … (Json data) __RequestVerificationToken=CfDJ8BSiPpdXlmRFvbl4LFJ0x7iHfmWBSdPblTwBjlLUq-We2oD60dKqBCYx4dUwXG5Gxprtl3lW2zzs4K8_iBf8eu0RQqOM928ANv1-16rcqizvYhUDFC5iaDo97wpqCsdFFxlmhiRaHW1zxhmEcwpYMrpZWBnzUbjGkTa-qUSs5GfuT2MwJGEWWYqyz7D95RRJVA

The API call returns a 200, but then the web page shows a 400 Bad Request. From Fiddler: 143 200 HTTPS localhost:7164 /api/ShareAllocations 144 400 HTTPS localhost:7164 /FarmAllocation/Manage

For comparison purposes, I’m showing the body of a submit in .net core. The key value pair for the anti forgery token looks the same to me.

SENIOR_LIVING_FACILITIES.FACILITY_ID=0&SENIOR_LIVING_FACILITIES.FACILITY_NAME=n&SENIOR_LIVING_FACILITIES.ADDRESS=&SENIOR_LIVING_FACILITIES.CITY=&SENIOR_LIVING_FACILITIES.STATE=ME&SENIOR_LIVING_FACILITIES.ZIP=&SENIOR_LIVING_FACILITIES.CONTACT_NAME=&SENIOR_LIVING_FACILITIES.CONTACT_ROLE=&SENIOR_LIVING_FACILITIES.PHONE=&SENIOR_LIVING_FACILITIES.EMAIL=&__RequestVerificationToken=CfDJ8BSiPpdXlmRFvbl4LFJ0x7iHfmWBSdPblTwBjlLUq-We2oD60dKqBCYx4dUwXG5Gxprtl3lW2zzs4K8_iBf8eu0RQqOM928ANv1-16rcqizvYhUDFC5iaDo97wpqCsdFFxlmhiRaHW1zxhmEcwpYMrpZWBnzUbjGkTa-qUSs5GfuT2MwJGEWWYqyz7D95RRJVA