Vale

Vale turns a writing style guide into checks that run in the editor and in CI. It ships almost no opinions of its own. A style is a folder of YAML rules, each built on one of 12 checks: existence flags listed words or patterns, substitution suggests a replacement, capitalization checks headings, readability scores a grade level with formulas such as Flesch-Kincaid and SMOG, spelling uses Hunspell dictionaries, and script runs custom logic. A .vale.ini file says which styles apply to which files, and vale sync downloads published packages such as Microsoft’s and Google’s style guides, proselint, write-good and alex.

What sets it apart is that it reads documents, not raw text. Markdown, AsciiDoc, reStructuredText, HTML and other formats go through a real parser, so a rule can target headings, lists or table cells, and code spans, URLs and fenced blocks are skipped. It lifts comments and docstrings out of source code with tree-sitter grammars, and “views” point it at the prose inside an OpenAPI file, a notebook or a commit message. It is a single Go binary that runs offline. Recent releases added rule inheritance, a standard library of rules (Std) and Voices, a package that turns the instructions people give LLMs about tone, such as “don’t hedge” or “no puffery”, into rules that check every draft.