Not long ago, I heard about this app called Hemingway. It's an algorithm designed to make a writer's style more like that of Ernest Hemingway. You copy and paste a piece of writing, and the program will tell you which sentences are hard to read, which sentences are really confusing, where you have too many adjectives and adverbs, and where you're using the passive rather than active voice.
Turns out it doesn't always work so well. There was a news article about how the program found errors when faced with samples of Hemingway's own writing.
Is the Hemingway app trustworthy at all? I say yes, with some fine print. Hemingway is not designed to make you a better storyteller. Sorry, folks, but you still have to provide the brain sweat. What the program will do is help economize your writing. Its creators stress that the program isn't designed to know when you intentionally break the rules, when you really do want that adjective.
I've used Hemingway since I first heard about it in February. It's helped me trim the fat on projects that have a specific word count such as reviews and short stories. I've also noticed that it's got me thinking more about active than passive sentences, though passive ones still slip through from time to time.
It is just a tool, and it's feedback is no different than suggestions you'd get from the spell-check on your word processor. You have the luxury of using it or ignoring it.