I kept seeing rule files that look fine but don’t do what people think. A .mdc with a description but no globs that never loads where you expect, an AGENTS.md past Codex’s 32 KiB limit that gets cut without a word, or a “never do X” line that’s only a request.
So I built a small checker. Paste a .cursor/rules/*.mdc, .cursorrules, AGENTS.md, CLAUDE.md or Copilot instructions file, pick where it sits (repo root, subfolder, home folder), and it shows:
- Which agents load it from that spot (Cursor, Claude Code, Codex, Copilot, Antigravity)
- What gets cut for length
- Frontmatter that decides loading (Cursor’s four load modes, Copilot’s applyTo)
- Lines no agent enforces, plus the hook, deny rule or linter config that would actually hold them
- Stuff that shouldn’t be there: secrets, duplicate lines, directory trees, “for now” rules
It runs in your browser and nothing you paste leaves the page. Free, no signup:
Would love feedback, especially on cases where Cursor’s loading behaves differently than what it reports.