Using an element of an array as match_field in enrich policy

[mustafa_savran]

I have been trying to use the element of an array as match_field in enrich policy but I didn't achieve this.
I have an array contains a bbox, a multi polygon and geo point respectively and I mapped this array as geo_shape.

"geometries": {
           "type": "geo_shape"
        }

I am trying to create a policy like this:

PUT /_enrich/policy/coor_policy
{
    "geo_match": {
        "indices": ["geometry_index"],
        "match_field": "geometries[1]",
        "enrich_fields": ["city_name"]
        
    }
}

But it constantly give this error:

"Could not traverse mapping to field [geometries[1]]. Could not find the [geometries[1]] field under [root]"

I have tried different kind of things but nothing worked.
When I write "match_field": "geometries", It works but I don't know which one is used in the array.