Is the output grammatical or well-formed in the target language? Using an interlingua should be helpful in this regard, because with a fixed interlingua one should be able to write a grammatical mapping to the target language from the interlingua.
Does the output conform to the grammatical standards of the target language, taking into account its specific linguistic features and conventions? Using an intermediary language can help create a translation that is not only grammatically correct but also contextually appropriate for the target language.