AWS OpenSearchException: Request failed: [parse_exception] missing suggestion object

Question

Hej,

I am currently implementing a service which calls an OpenSearch Domain for suggestions but I am currently receiveing the follwing exception:

 org.opensearch.client.opensearch._types.OpenSearchException: Request failed: [parse_exception] missing suggestion object
    at org.opensearch.client.transport.aws.AwsSdk2Transport.parseResponse(AwsSdk2Transport.java:486)
    at org.opensearch.client.transport.aws.AwsSdk2Transport.executeSync(AwsSdk2Transport.java:393)
    at org.opensearch.client.transport.aws.AwsSdk2Transport.performRequest(AwsSdk2Transport.java:191)
    at org.opensearch.client.opensearch.OpenSearchClient.search(OpenSearchClient.java:1219)
    at com.heiland.searchservice.repository.AbstractOpenSearchRepository.autocomplete(AbstractOpenSearchRepository.java:46)
    ... 176 common frames omitted

Here is my call: final SearchRequest request = SearchRequest.of(s -> s.index(searchIndex()).suggest(factory.createSuggester(query)));

Here is the implementation of the method createSuggester():

    public Suggester createSuggester(final String query) {
        final CompletionSuggester completion = CompletionSuggester.of(c -> c.field("suggestions"));
        final FieldSuggester fieldSuggester = FieldSuggester.of(f -> ((FieldSuggester.Builder) f.completion(completion)).prefix(query));
        return Suggester.of(s -> s.suggesters("autocomplete", fieldSuggester));
    }

The Suggester represents this call, which works fine:

GET index/_search
{
  "suggest": {
    "autocomplete": {
      "prefix": "Haut",
      "completion": {
        "field": "suggestions"
      }
    }
  }
}

Does anyone has an idea of what am I doing wrong? The OpenSearch Documentation is, in this case, not really helpful....

I tried to make a completion call. I expected a Suggestion Result.