Questions & Answers about Das steile Dach ist kaputt, oder?
Why does the adjective steil have an -e at the end here?
Because the adjective comes directly before the noun Dach, it needs an ending. After the definite article das (the) in the nominative (subject) case, the adjective simply takes an -e. So steil becomes steile.
Why doesn't the word kaputt get an ending like steile does?
In German, adjectives only take an ending when they are placed directly in front of the noun they describe. When an adjective comes after a verb (like ist) to describe the subject, it stays in its basic dictionary form. That is why kaputt has no ending.
Doesn't oder normally mean 'or'? Why is it translated as 'isn't it' here?
You are right, oder usually translates to 'or'. However, when it is placed at the very end of a statement after a comma, it acts as a quick tag question. It is the German equivalent of asking 'right?', 'isn't it?', or 'don't you?' to get confirmation from the listener.