Review Code

Review Code

Review a target and report findings. Each finding is rated by severity (how bad if it happens), likelihood (how often the bad path actually runs), and a worth-fixing verdict derived from both — plus a high-level fix when worth fixing. This skill reports only; it never edits code unless the user explicitly asks afterward.

Resolve the target

Pick the target from the argument. Default to diff when none is given.

1. diff (default) — review local work on the current branch. The change can live in three places at once — uncommitted edits in the working tree, local commits not yet pushed, and commits already pushed to the branch — and is usually a mix. Gather and review all three together. Anchor the comparison on where the branch forked from its base branch, not on the branch's own remote — otherwise commits drop out of the diff once they are pushed. Include new untracked files, which a plain diff omits.
2. pr (or a PR URL) — review a GitHub PR: its diff plus enough PR context (title, description, base branch) to judge intent. If the GitHub CLI is unavailable, say so and fall back to diff.
3. all / codebase — review the whole repository. State the scope you can realistically cover and prioritize entry points, core logic, and recently changed files. Note anything skipped.
4. `` — a file or directory argument scopes the review to that path.

For a diff/PR, review the changed lines plus enough surrounding context to judge them (callers, related functions). A bug is in scope even if the changed line only exposes it.

Review lens (in priority order)

1. Correctness — logic errors, off-by-one, nil/null derefs, wrong conditionals, race conditions, unhandled errors, incorrect API usage, broken edge cases.
2. Security — injection, missing authz/authn, secrets in code, unsafe deserialization, path traversal, unvalidated input.
3. Data & resources — leaks (fd/memory/goroutine), unbounded growth, missing transaction boundaries, N+1 queries.
4. Performance — needless allocations, O(n²) on hot paths, blocking calls in loops.
5. Maintainability — duplication, dead code, unclear naming, missing-but-needed tests. Report these only when they materially hurt; do not pad the report with style nits.

Do not invent problems. If the code is clean, say so. Prefer a few high-confidence findings over many speculative ones.

Rating each finding

Severity — impact if the bad path executes:

• Critical — data loss/corruption, security breach, crash on a common path, wrong results affecting users or money.
• High — wrong results or crash under realistic conditions; security issue needing some precondition.
• Medium — degraded behavior, perf regression, or a correctness bug on a rare path.
• Low — style, readability, minor inefficiency with no functional impact.

Likelihood — how often the triggering condition is actually met:

• High — hit by normal usage or common inputs.
• Medium — uncommon but realistic inputs/timing/config.
• Low — requires rare, adversarial, or near-impossible conditions.

Worth fixing — derived from severity × likelihood, adjusted for fix cost:

                 Likelihood
Severity     High        Medium      Low
Critical     Yes         Yes         Yes
High         Yes         Yes         Judgment call
Medium       Yes         Judgment    No (note only)
Low          Judgment    No          No

• Yes — recommend fixing; include a fix.
• Judgment call — explain the trade-off (fix effort vs. payoff) and give a recommendation; include a fix.
• No — note it for awareness; omit the fix or keep it to one line.

Bump a Judgment call to Yes when the fix is trivial; drop toward No when the fix is large/risky relative to payoff. State the reason when you override the matrix.

Report format

Lead with a one-line summary and a table sorted by worth-fixing (Yes first), then severity. Then one block per finding.

**Reviewed:**  — 
**Summary:** 

| # | Finding | Severity | Likelihood | Worth fixing |
|---|---------|----------|------------|--------------|
| 1 |  | High | High | Yes |
| 2 |  | Low | Medium | No |

Then for each:

### 1. 
- **Location:** `path/to/file.ext:42`
- **Category:** correctness | security | resources | performance | maintainability
- **Severity:** High — 
- **Likelihood:** High — 
- **Worth fixing:** Yes
- **Issue:** 
- **Fix:** 

End with: **Not worth fixing right now:** if any No/low items were folded out, so nothing is silently dropped.

Verification procedure

Before sending the report, check:

1. Every finding cites a real location (file:line) you actually inspected — no hypothetical line numbers.
2. Severity and likelihood are independent — do not collapse them ("it's bad so it's likely"). A Critical-but-Low and a Low-but-High are both valid and common.
3. The worth-fixing verdict matches the matrix, or you stated why you overrode it.
4. Every "Yes" and "Judgment call" has a concrete fix; every fix is high-level (approach, not a finished diff).
5. No fix was applied to the working tree — this skill reports only.
6. Clean code is reported as clean. If you found nothing worth fixing, say that plainly instead of manufacturing Low findings.

Common mistakes to watch for

• Conflating severity with likelihood. A SQL injection reachable only by an admin is High severity / Low likelihood — rate the two axes separately.
• Reviewing only changed lines. A diff can introduce a bug whose root cause is in unchanged code a caller away; read enough context to judge it.
• Padding with style nits. Low/Low findings drown the real issues. Fold them into the one-line "not worth fixing" list.
• Writing fixes as full patches. Keep fixes high-level; the user asked for findings, not edits.
• Silently capping a codebase review. If you could not cover everything, say what you skipped and why.
• Missing changes that were already pushed. Comparing against the branch's own remote hides commits once they are pushed. Anchor on the base-branch fork point so committed, pushed, and uncommitted work are all reviewed.
• Forgetting untracked files. Brand-new files often fall outside a plain diff — pull them in or they go unreviewed.
• Guessing the target state. If the tools return nothing or error out, report that instead of reviewing an empty target.

Source & license

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

• Author: lwlee2608
• Source: lwlee2608/agent-skills
• License: MIT

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