pg_isready mandatory parameters?

I found this in PG14 è

bash-4.4$ ./pg_isready --version

pg_isready (PostgreSQL) 14.2

bash-4.4$ ./pg_isready

/var/run/postgresql:5432 - no attempt

bash-4.4$ ./pg_isready -h localhost

localhost:5432 - no attempt

bash-4.4$ ./pg_isready -h localhost -p 5432

localhost:5432 - no attempt

bash-4.4$ ./pg_isready -h localhost -p 5432 -d postgres

localhost:5432 - no attempt

bash-4.4$ ./pg_isready -h localhost -p 5432 -d postgres -U postgres

localhost:5432 - accepting connections

I always thought all parameters are optional? No?

Thanks,

Markus