Check

Output style (plain words, no dashes, no hyphens)

Write everything this skill produces, files and messages alike, in plain simple language. Keep technical terms that carry real meaning; explain each in plain words. Never use a dash or a hyphen as punctuation: no em dash, no en dash, and no hyphenated compounds. Write read only, not read-only. Say it in simple words, or reword the sentence. Code, file paths, command flags, and values other skills match on keep their hyphens. Use short sentences, commas, or parentheses. Clear beats clever.

What this skill does

/check is the gate before merge. It confirms a change is sound in two different ways, run as two modes; they are separate jobs and you usually run both, verify first:

• verify (runtime proof): run the real app and watch the change behave. Proves the feature actually works and conforms to the spec (every acceptance criterion met, every specced surface built), which green tests never reveal. Read only on code, owns no durable files. Runs on the main thread. Typically after /develop.
• review (fresh model code review): a rigorous senior read of the diff, on a different model than wrote the code, because a model reviewing its own output shares its blind spots. Writes findings ranked by severity to docs/reviews/. Read only on code. Typically before opening a PR.

Neither mode edits your code. verify points failures at /debug or /develop; review reports findings for the implementer to fix.

Pick the mode (route before doing anything else)

Read the argument and route:

• Starts with verify (or run) → runtime proof. Read modes/verify.md and follow it fully. Pass any remaining arguments (a feature name, a scope) through.
• Starts with review → code review. Read modes/review.md and follow it fully. Pass the review steering through unchanged (e.g. /check review with opus, /check review uncommitted).
• No mode word, or ambiguous → ask once which one, capability first (a picker where the agent has one, else plain text): question "Which check?", header "Check", options verify: run the real app and prove it works (recommended right after building) · review: a fresh-model read of the diff before a PR. The picker appends its own free text option; add it explicitly in a plain text fallback. Then read that mode's file and follow it.

Do not mix the two in one run. If the engineer clearly wants both, do verify first (confirm it works), then offer review.

Portability (any OS, any agent)

Any Agent Skills client on macOS, Linux, or Windows. git is the only required CLI and behaves the same everywhere; other shell snippets are POSIX reference, not literal scripts, so use your agent's own cross platform file, process, and browser tools and apply branching logic yourself. Each mode file adds its own portability notes (browser/HTTP driving for verify, the cross model spawn and bundled file handling for review). No subagent support falls back to running the work inline, noted per mode.

Bundled files live in this skill's folder: modes/verify.md, modes/review.md, and (for review) review-agent-prompt.md and review-guide.md. Read only the mode file you routed to; the main agent resolves the review bundled files to absolute paths when it spawns the reviewer.

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: jsmastery-pro
• Source: jsmastery-pro/skills
• License: MIT
• Homepage: https://jsmastery.com

Install and usage instructions live in the source repository linked above.