I try to create a webhook using curl

Hi I try to create a webhook by using a curl command as described here:

The command look like this:
jsonconfig= cat ./preview-webhook-staging.json

curl -X POST \
     -H "Authorization: Bearer CFPAT-***************" \
     -H "Content-Type: application/vnd.contentful.management.v1+json" \
     -d "$jsonconfig" \
    https://api.contentful.com/spaces/******/webhook_definitions

the content of the config json looks like this:

{
    "name":"TopLevel Content Trigger STAGING",
    "url":"http://www.myhost.de:30030/explore-cms/api/v1/contentful/webhook/toplevel-content",
    "topics":[
      "Entry.save",
      "Entry.auto_save"
    ],
    "filters":[
      {
        "equals":[
          {
            "doc":"sys.environment.sys.id"
          },
          "ex-icke-master"
        ]
      },
      {
        "in":[
          {
            "doc":"sys.contentType.sys.id"
          },
          [
            "standardPage"
          ]
        ]
      }
    ],
    "transformation":{
      "body":{
        "spaceId":"{ /payload/sys/space/sys/id }",
        "environment":"{ /payload/sys/environment/sys/id }",
        "cmsId":"{ /payload/sys/id }",
        "contentTypeId":"{ /payload/sys/contentType/sys/id }",
        "publishedVersion":"{ /payload/sys/publishedVersion }",
        "version":"{ /payload/sys/version }",
        "publishedCounter":"{ /payload/sys/publishedCounter }",
        "archivedVersion":"{ /payload/sys/archivedVersion }",
        "gcType":"{ /payload/fields/gcType/de-AT }",
        "gcid":"{ /payload/fields/gcid/de-AT }"
      }
    },
    "active":true,
    "headers":[
      {
        "key":"X-MY-BEARER-TOKEN",
        "value":"WTIE****************",
        "secret":true
      }
    ]
  }

but I get this error :

{
  "requestId":"b6834aa0-c74e-4535-8595-cba38359eb3f",
  "details":{
    "key":"resource"
  },
  "sys":{
    "type":"Error",
    "id":"MissingKey"
  }

Can someone understand which Key is missing here?

the solution for the annoying / meaningless error message, use JS instead of curl.
@contentful-admin fix the documentation, for CURL it does not work