Whether we like it or not, our jobs are what we are. The poem uses near rhyming throughout, not one real rhyme. The near-rhyme provides a lighthearted tone. Though the poem was written in an amusing form, it is wrought with serious undertones. The word toad itself is very descriptive.
Toad brings to mind squatty, blundering and something that is very heavy or serious.
The toad is compared to work. The author examines why he cannot live by his wit in the middle of the poem. He looks at talkers and the poor, and wonders why he cannot do that. Toward the end, the attitude shifts back toward the inevitable truth that he must work. He determines he has a bit of the toad in him, as he is too conservative to just toss everything away.