Four modes, each a fixed rule set
Clearer expands common contractions (don’t to do not, it’ll to it will) and swaps jargon for the plain word behind it (utilize to use, in order to to to). Concise cuts the filler that pads a sentence out (due to the fact that to because, at this point in time to now) and drops padded intensifiers. Formal does the written-up pass (gonna to going to, kids to children). Friendly is the mirror image on purpose: it contracts the long forms back into the way people actually talk.
The mode is a menu, not a recommendation: the page never picks a mode for you, because the right voice is the reader’s judgment, not the tool’s. Run the same text through all four and keep the one that fits the document.