You wrote correctly. Just this phrase can be used with two choices:
Как ты думаешь, это хорошо?;
Что ты думаешь, это хорошо?;
And it has the same meaning.
I think your version will be added in the future. What about the rules of the use of these words (what - что and как - how) - their meanings are the same as in English
I translated this sentence as 'What do you think, is it all right?' but was corrected to "What do you think, is this fine.' Isn't 'all right' a possible English translation for 'хорошо' and isn't 'is it' a possible translation for 'это'? (Note: the hover translation of 'это' lists 'this, it is, that' as translations.)