A linter is a software utility that flags “suspicious usage” in software. Although linters are used by developers mostly to write more bug-free code, there are a few utilities emerging that work with documentation. They could be useful if you’re writing Web pages, markdown files or XML files.
Write good checks for passive voice, repeated words, adverbs, weasel words, wordy phrases and unnecessary words, and cliches.
Retext Mapbox Standard is a testing tool that checks for common grammar, sensitivity and simplicity errors.
Hemingway is an application, rather than a utility. You can paste your content into Hemingway for an assessment of its clarity. Hemingway will give your content a readability score and identify sections that are hard to read.