You can call the DescribeSearchIndex operation to query the description of a search index for a table, including fields and configurations of the search index.

Sample code:

index_meta, sync_stat = client.describe_search_index(table_name, index_name)
print json.dumps(index_meta, default=lambda x:x.__dict__, indent=2)
print json.dumps(sync_stat, default=lambda x:x.__dict__, indent=2)