In https://docs.dagster.io/concepts/configuration/config-schema#using-ops I see this example, but it is missing the part where you actually set the value and pass it to the operation:

from dagster import op, Config

class MyOpConfig(Config):
    person_name: str

@op
def print_greeting(config: MyOpConfig):
    print(f"hello {config.person_name}")  # noqa: T201