Search a contact by a custom field with API

Hello, i have a custom field created with an id.
I need to search by that id and get the returning contact as i know each field is going to be unique.
How can i do this with the API? Contact search endpoint don’t have any query for custom fields so don’t know how to do this.

Thanks!

The API endpoint that returns field values is https://{{yourAccountName}}.api-us1.com/api/3/fieldValues. (If you want all customFields) and https://{{yourAccountName}}.api-us1.com/api/3/fieldValues/{id} (If you already know the customField id) At this time we do not have filtering available on this endpoint, so the best way to do this is to retrieve the list of customFields and values, iterate through the results, and find value you need.