How can I get the master table for contracts types?

I'm new in the use of the API and I'm having some troubles getting specific information. There is one option called "Reads all Reference contracts" which returns among others the field "es_contract_type_id" whis is an id. How can I get the master table to get the translation of that id to the description like "undefined" or other values, not the id.

This applies to others fields like that, id with no related information of how getting the description.

Thank in advance