Deals Search return custom_fields with no keys

I’m trying to perform an API call to search deals by custom field, which works, but the returned “custom_field” array does not contain the field key, only the values in one long array.
How should I identify which value belongs to my fields?

Here’s an example from the /v1/deals enpoint:

An the one from the /v1/deals/search:

Thanks in advance!

no one that uses this endpoint and ran into that?