Green’s Dictionary of Slang

(US black/teen) excellent, wonderful.

1971		H.E. Roberts Third Ear n.p.: toast adj. good; fine; acceptable.
1994		J. Wambaugh Finnegan’s Week 128: He’s ... toast.
1996		Eble Sl. and Sociability 83: Toast means ‘excellent’; and stone means ‘thorough, perfect.’.