Adding Form field Signature to a PDF using REST API v6

I have been attempting to use the v6 API to create form fields on a uploaded PDF. Basically, I’m trying to do the v6 REST API version of this:

https://helpx.adobe.com/sign/kb/place-form-fields-in-a-document-using-rest-api-adobe-sign.html

Is there an update of this or a resource example?

It creates the agreement just fine, but no field ever gets created. I have tried many iterations. Here’s the body I was working on in a Logic App:

{

    "fileInfos": [{

        "transientDocumentId": "XXXXXXXXXXXX"

    }],

    "formFieldGenerators": [{

        "formFieldDescription": {

            "contentType": "SIGNATURE_BLOCK",

            "inputType": "SIGNATURE"

        },

        "anchorTextInfo": {

            "anchorText": "Test",

            "anchoredFormFieldLocation": {

                "height": 130,

                "width": 100

            }

        },

        "formFieldNamePrefix": "kdc_",

        "participantSetName": "KDC1",

        "generatorType": "ANCHOR_TEXT"

    }],

    "name": "kdc",

    "participantSetsInfo": [{

        "name": "KDC1",

        "order": 1,

        "role": "SIGNER",

        "memberInfos": [{

            "email": "myRedactedEmail@email.com"

        }]

    }],

    "signatureType": "ESIGN",

    "state": "IN_PROCESS"

}