If,however, you are unsure of your own grammar expertise, they are uniformly harmful. RightWriter analyzes your writing for a variety of things and gives it a grade-level readability score. People often misunderstand and think that if RW says they have written at 7th grade level that they have written seventh grade work. The score means their writing would be clear to a good seventh grader. A score of 7th grade writing is far better than a score of 14th grade because 14th grade is probably jargon-y gobbledegook and 7th grade writing is good general English, understandable to ordinary folks.
Handbooks are very useful for checking grammar and punctuation rules.
Your CommonSpace program has an on-line handbook. Although I did not require you to buy one in book form this semester, you should soon purchase one. They go out of date about every twenty years.