SF_13.3 - https://www.progress.com/documentation/sitefinity-cms/headless-development/filter-and-sort-operations

SelectWhatFieldsToReturnFromAnEntity.json

{
    "@odata.context": "http://localhost:4242/api/default/$metadata#newsitems(Title,Summary)/$entity",
    "Title": "Sample news item",
    "Summary": "Lorem Ipsum"
}