Добрый день, подскажите почему возвращается ошибка 400 Bad Request?

{
  "data" : null,
  "error" : true,
  "errorText" : "Invalid request format",
  "additionalErrors" : { }
}

Запрос:

POST https://content-api-sandbox.wildberries.ru/content/v2/cards/upload

{
  "subjectID" : 5283,
  "variants" : [ {
    "vendorCode" : "1918091",
    "title" : "Title Test",
    "description" : "Descr Test",
    "brand" : "Ikon",
    "characteristics" : [ {
      "id" : 244925,
      "value" : [ "нет" ]
    }, {
      "id" : 14177446,
      "value" : [ "Ikon" ]
    }, {
      "id" : 15002677,
      "value" : [ "нет" ]
    }, {
      "id" : 244922,
      "value" : [ "лето" ]
    }, {
      "id" : 15001206,
      "value" : [ "нет" ]
    }, {
      "id" : 15001208,
      "value" : 98
    }, {
      "id" : 15001207,
      "value" : [ "V" ]
    }, {
      "id" : 5023,
      "value" : [ "Model Name Test" ]
    }, {
      "id" : 244965,
      "value" : [ "r17" ]
    }, {
      "id" : 244948,
      "value" : [ "55" ]
    }, {
      "id" : 244928,
      "value" : [ "215" ]
    }, {
      "id" : 88953,
      "value" : 0
    }, {
      "id" : 89064,
      "value" : 0
    }, {
      "id" : 90745,
      "value" : 0
    }, {
      "id" : 90846,
      "value" : 0
    }, {
      "id" : 90849,
      "value" : 0
    }, {
      "id" : 378533,
      "value" : [ "нет" ]
    }, {
      "id" : 5522881,
      "value" : [ "нет" ]
    }, {
      "id" : 14177451,
      "value" : [ "нет" ]
    }, {
      "id" : 14177453,
      "value" : [ "нет" ]
    }, {
      "id" : 15000001,
      "value" : [ "нет" ]
    }, {
      "id" : 15001135,
      "value" : [ "нет" ]
    }, {
      "id" : 15001136,
      "value" : [ "нет" ]
    }, {
      "id" : 15001137,
      "value" : [ "нет" ]
    }, {
      "id" : 15001138,
      "value" : [ "нет" ]
    }, {
      "id" : 15001209,
      "value" : [ "нет" ]
    }, {
      "id" : 15001405,
      "value" : [ "нет" ]
    }, {
      "id" : 15001650,
      "value" : [ "нет" ]
    }, {
      "id" : 15001706,
      "value" : [ "нет" ]
    }, {
      "id" : 15002678,
      "value" : 0
    }, {
      "id" : 15002679,
      "value" : [ "нет" ]
    }, {
      "id" : 15003293,
      "value" : [ "нет" ]
    } ],
    "sizes" : [ {
      "price" : 1234567
    } ]
  } ]
}