When you are reading documentation on the documentation page, at the upper-right, there is a selection for either Chat Completions or for the newer Responses endpoint.
In the API documentation, the left bar of endpoints will require discovery of each endpoint in the list.
text → format is the Responses endpoints version of Chat Completions’ response_format parameter.
While each would have the same “schema” ultimately placed, the structure of the metadata object container for signifying the type, name and whether it is strict is also different between endpoints.