I hope english is the correct languge for posting here.
Consider the following wrong german sentence:
Ich habe eine Termin.
The word "Termin" has genus masculin, which is hard
to remeber especially for people from Spain, because in
Español (Spanish) words ending with "in" are usually feminin.
So the correct sentence would be:
Ich habe einen Termin.
I've an employee from spain working here in Germany and he
tried languagetool 2.1 today and he was a little disappointed
to see, that this kind of error was not discovered by languagetool.
On the other hand he is good Java programmer and might be
able to contribute something if pointed in the right direction.
Best regards, Peter.