sharp-pen

sharp-pen is an open-source proofreading tool that runs inside an AI assistant such as Claude, ChatGPT, Codex or Copilot. Given a draft, it produces an interactive two-pane review page: the original text on the left, suggested corrections on the right, with each difference highlighted and clickable. Changes are accepted individually; where more than one phrasing is possible, alternatives are offered in a dropdown. Nothing is applied until the user accepts it, and the original text is never edited in place.

Suggestions are split into two passes that can be toggled in the page: spelling and grammar (typos, agreement, prepositions, articles, comma splices), and sentence construction (fragments, broken parallelism, buried points, sentences that trail off). The tool is constrained to correcting form rather than substance — it does not change what a sentence claims, remove hedges, or alter tone.

It is distributed as an agent skill and plugin. The review page is a single self-contained HTML file with no external resources or network requests; the draft is processed only by the assistant the user already uses. Free, MIT-licensed, no account required. A live demo is available without installation on https://nobbettt.github.io/sharp-pen/.