וַיֹּ֣אמֶר אֵלָ֔יו הִנֵּה֙ נָשָׂ֣אתִי פָנֶ֔יךָ גַּ֖ם לַדָּבָ֣ר הַזֶּ֑ה לְבִלְתִּ֛י הָפְכִּ֥י אֶת־הָעִ֖יר אֲשֶׁ֥ר דִּבַּֽרְתָּ׃
And he said unto him: ‘See, I have accepted thee concerning this thing also, that I will not overthrow the city of which thou hast spoken.
Rashi on Genesis
גם לדבר הזה CONCERNING THIS THING ALSO — Not only will you be saved, but I will also save the whole city for Your sake.
Radak on Genesis
ויאמר אליו הנה נשאתי פניך, from this verse we may deduce that when G’d dispatches an angel on a major mission, He gives the angel some discretion in the manner in which he is to carry out the task assigned to him. The angel or angels may use their own intelligence in this respect. Clearly, an angel is not like a golem, but is an intelligent being.
Haamek Davar on Genesis
Also … regarding this. Hashem agreed not to overturn Zoar at all.