You may want to experiment by creating a temporary pond that fills only after rain. This is the type of pond many species of frogs prefer. A clean environment. Chemicals should be avoided in your garden. Frog skin is quite thin and easily absorbs chemicals.
Frogs are also likely to eat poisoned insects with fatal consequences.
By making a few changes to your garden, the frogs will come all by themselves. If they are slow to arrive, play a tape of frog calls on a hot humid night. Once one arrives, the others will follow quickly and then you will have your very own frog chorus. If you have a swimming pool , there is a good chance that frogs will occasionally drown in it. Frogs are attracted by the high humidity and the gardens surrounding of the swimming pool.