The problem with grammar checkers in general is that they can't distinguish between:

Atlantis flies like a 'plane.
Time flies like an arrow.
Fruit flies like a banana.

(Apologies to gumpu, whose answer I hadn't seen when I wrote this - this is clearly a good example :-)

And indeed, code to distinguish between generalisations of those three examples alone would be more trouble to code than it's worth (unles you're being paid to research natural language, in which case you're lucky). There are modules to conjugate English verbs and decline English nouns, but this will only help your program to write simple grammatical sentences, such as Colourless green ideas sleep furiously. :-)

M$'s grammar checkers commit further errors by producing entirely spurious queries, such as 'passive voice' (one of the few parts of speech their system usually spots), which it regards as wrong! The same system also routinely argues 'subject-verb agreement' errors where none exist, and (if the right 'feature' is enabled) can prevent you using any gender-specific language.

Tiefling (and remember - verbing weirds language)