"This rare frog only ventures out in the rain. When cooked with monster parts, the elixir it produces will temporarily increase your maximum stamina."
Hyrule Compendium

The Tireless Frog is an item from The Legend of Zelda: Breath of the Wild. Link can cook with it and monster parts to create Enduring Elixir. Cooking them with other ingredients will usually result in Dubious Food. Tireless Frogs more commonly appear in ponds and rivers during rainy weather.

See also