Calculate the percentage of the total documents across all buckets

OpenSearch
1

Versions (relevant - OpenSearch/Dashboard/Server OS/Browser): OpenSearch 2.16

Describe the issue:
My DSL to get top 5 common values for the field ‘Dest’ in database and thier percent of total:

common values for the field

GET /opensearch_dashboards_sample_data_flights/_search
{
  "size": 0,
  "aggs": {
    "total_count": {
      "global": {}, 
      "aggs": {
        "total_count_dest": {
          "value_count": {
            "field": "Dest"
          }
        }
      }
    },
    "top_dest": {
      "terms": {
        "field": "Dest",
        "size": 5,
        "order": {
          "_count": "desc"
        }
      },
      "aggs": {
        "percent_of_total": {
          "bucket_script": {
            "buckets_path": {
              "count": "_count",
              "total": "total_count['total_count_dest']"
            },
            "script": "params.count / params.total * 100"
          }
        }
      }
    }
  }
}

Configuration:

Relevant Logs or Screenshots:
But I got error:

{
  "error": {
    "root_cause": [
      {
        "type": "action_request_validation_exception",
        "reason": "Validation Failed: 1: No aggregation found for path [total_count['total_count_dest']];"
      }
    ],
    "type": "action_request_validation_exception",
    "reason": "Validation Failed: 1: No aggregation found for path [total_count['total_count_dest']];"
  },
  "status": 400
}

Help my change my dsl to return data as expect. Thank very much.