Adding an event to an opportunity

AddEvent = sf_api_call('/services/data/v40.0/sobjects/Event', method = 'post', data={
    #'Type': 'Meeting', # seems not required
    'Subject': 'Qualification meeting',
    'OwnerId': "0050Y000000PIONQA4",
    'ActivityDate': '2017-07-24T00:00:00.000Z',
    'IsAllDayEvent': True,
    'WhoId': "0030Y00000KAABsQAP", #from doc: "represents a human such as a lead or a contact"
    'WhatId': "0060Y0000077iDGQAY", #from doc: "represents nonhuman objects such as accounts, opportunities, campaigns, cases, or custom objects"
    'Description': 'blablabla'
})