The speaker begins by addressing a toad that stares back at him, calm and unbothered. He describes it closely: the warty, ridged skin, the way it squats rather than sits, the glands swollen with poison. Then comes a small, knowing line, "Think I didn't know?", as if the toad might be assuming he's ignorant of its danger, or expecting him to be afraid.
He isn't. The poem turns into an invitation. The speaker tells the toad to go forth without fear and to breed, and he lists what he can offer: grass, a dried leaf, a twig, the shade of big trees. The last line points to a place for the toad's children, which the poem calls "Kunthi". I can't say for certain what that refers to, but it seems to be a name or a spot set aside for them.
The mood is warm, amused and quietly tender. A creature people often find ugly or threatening is treated with respect, even affection.