GraphQL mutation metaobjectUpdate error 400

[FritzF]

Hi, we're trying to update a metaobject including ratings for our store via the GraphQL API. We're using the shopify-api-node by monei to do this. Receiving data such as the metaobject's id was successful, but we can't seem to update the metaobject's data.

This is our code:

  const query = `mutation metaobjectUpdate($id: ID!, $metaobject: MetaobjectUpdateInput!) {
    metaobjectUpdate(id: $id, metaobject: $metaobject) {
      metaobject {
        rating
        count
      }
      userErrors {
        field
        message
        code
      }
    }
  }`;

  const variables = `{
    "id": "gid://shopify/Metaobject/2085388555",
    "metaobject": {
      "fields": [
        {
          "key": "rating",
          "value": 4.1
        },
        {
          "key": "count",
          "value": 700
        }
      ]
    }
  }`;

  const test = `{
    metaobjects(type: "reviews", first: 3) {
      edges {
        node {
          id
          handle
        }
      }
    }
  }`;

  return await shopify.graphql(query, variables);

And this is the response:

HTTPError: Response code 400 (Bad Request)
    at Request.<anonymous> (/Users/<hidden-stuff>/node_modules/got/dist/source/as-promise/index.js:118:42)
    at processTicksAndRejections (node:internal/process/task_queues:95:5) {
  code: 'ERR_NON_2XX_3XX_RESPONSE',
  timings: {
    start: 1687252703717,
    socket: 1687252703718,
    lookup: 1687252703721,
    connect: 1687252703750,
    secureConnect: 1687252703788,
    upload: 1687252703788,
    response: 1687252703891,
    end: 1687252703891,
    error: undefined,
    abort: undefined,
    phases: {
      wait: 1,
      dns: 3,
      tcp: 29,
      tls: 38,
      request: 0,
      firstByte: 103,
      download: 0,
      total: 174
    }
  }
}

As you can see it's pretty useless. Does anyone see what we're doing wrong?