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Agent skill

Code Review

by TheDecipherist in TheDecipherist/claude-code-mastery-project-starter-kit

Review changed code for correctness, security, and maintainability with cited, severity-ranked findings.

MITAuto-check: notesDevelopment

Install Code Review

skills CLI
$ npx skills add TheDecipherist/claude-code-mastery-project-starter-kit --skill code-review -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install TheDecipherist/claude-code-mastery-project-starter-kit code-review --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/TheDecipherist/claude-code-mastery-project-starter-kit.git skills-src && mkdir -p .claude/skills && cp -r skills-src/.claude/skills/code-review .claude/skills/code-review && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
code-review
GitHub stars
338
Token cost
~1.1k tokens
SKILL.md length
562 words
Files
3 (incl. references)
Skills in repo
24
Repo updated
First seen
Licence
MIT

At a glance

Review changed code for correctness, security, and maintainability with cited, severity-ranked findings.

  • Works in 6 steps: Scope → Cheap wins first (run tools before… → Read by diff size → …
  • Asked to review a diff
  • SKILL.md covers Priority order, 1. Scope, 2. Cheap wins first (run tools… and 3. Read by diff size, plus 6 more sections
  • Calls git, npm and cargo

What it does

Code Review is an agent skill from TheDecipherist/claude-code-mastery-project-starter-kit. Review changed code for correctness, security, and maintainability with cited, severity-ranked findings. Use when asked to review a diff, a PR, a commit, or named files, to audit code, or to check before merge. Runs isolated and read-only, reports findings, does not edit.

Its SKILL.md is about 1.1k tokens, which your agent loads only when the skill is triggered. The skill folder holds 3 other files, including reference files (for example `references/mongodb-checks.md` and `references/project-checks.md`).

It sits in Development, covering Code review. The repository describes itself as: The definitive starting point for Claude Code projects. Based on Claude Code Mastery Guides V1-V5. The licence is MIT.

When your agent uses it

  • Asked to review a diff
  • Check before merge

Example prompts

  • “/code-review”

Requirements

  • Pre-approved tools (allowed-tools): Read, Grep, Bash

Workflow steps

6 steps, taken from the step headings in SKILL.md.

  1. Scope
  2. Cheap wins first (run tools before reading)
  3. Read by diff size
  4. Project checks (highest priority)
  5. General checks
  6. Language checks (the high-value ones)

What it can do on your machine

Read from SKILL.md and the folder at commit 61fbb99. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves these tools, so the agent can use them without asking each time:

    • Read
    • Grep
    • Bash

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    Shell commands in SKILL.md call:

    • git
    • npm
    • cargo

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    No URLs in SKILL.md. Its commands use git and npm, which can reach the network depending on how they are called.

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Code Review loads about 1.1k tokens when it runs, and up to ~2.6k if it reads all its reference files. Until then it costs about 71 tokens; SKILL.md has 562 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~71
When it runs · the whole SKILL.md, loaded when a task matches
~1.1k
With references · SKILL.md plus every file in references/, read only if the agent opens them
~2.6k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check: notes

The automated check noted patterns worth knowing about, such as sudo or a known installer.

  • NotePre-approves every shell command (allowed-tools: Bash)SKILL.md
    allowed-tools: Read, Grep, Bash

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from TheDecipherist/claude-code-mastery-project-starter-kit at commit 61fbb99, republished under its MIT licence (© TheDecipherist). 562 words, ~1,118 tokens.

Download SKILL.mdSave it as .claude/skills/code-review/SKILL.md (or your agent's skills folder). This skill also uses 2 other files; get the full folder from GitHub.
name
code-review
description
Review changed code for correctness, security, and maintainability with cited, severity-ranked findings. Use when asked to review a diff, a PR, a commit, or named files, to audit code, or to check before merge. Runs isolated and read-only, reports findings, does not edit.
allowed-tools
Read, Grep, Bash
when_to_use
- User asks to review code, audit a file, or check a PR before merge - User says "review", "audit", "check this code", or "find issues" - Do NOT use for…
context
fork
effort
high

Code Review

You review like a senior engineer reviews a pull request: concrete findings, each tied to a line, each with a fix and a reason. No generic praise, no style nitpicking dressed up as risk. You report only. You do not edit code.

Priority order

When triaging what to flag and how hard, rank in this order:

  1. Security — secrets, injection, auth bypass
  2. Correctness — logic errors, race conditions, null risks
  3. Performance — N+1 queries, leaks, missing indexes
  4. Type safety — any, missing null checks, unsafe casts
  5. Maintainability — dead code, unclear naming (lowest)

If the code is good, say so. Do not invent issues to fill a report.

1. Scope

Establish what changed: git diff --name-only HEAD~1, or read the files named. Identify the primary concern (security, correctness, performance) and pull conventions from CLAUDE.md if present.

2. Cheap wins first (run tools before reading)

Run what the project supports, skip what's missing, never fail the review over a missing tool:

  • Dependency CVEs: npm audit / pip-audit / cargo audit
  • Secrets in the diff: grep changed files for assignments to keys, tokens, passwords with long literal values
  • Recent context: git log --oneline -5

3. Read by diff size

  • Under 20 files: read each changed file in full.
  • 20 to 100: read the diff, then deep-read the high-risk files (auth, payment, config, migrations, shared utilities, anything touching the data layer).
  • Over 100: ask for a narrower scope before proceeding.

4. Project checks (highest priority)

Read references/project-checks.md and apply every check in it. These are this codebase's hard rules: data access and driver discipline, StrictDB-or-native, API versioning, service boundaries. Violations here are CRITICAL by default, they are the failures generic review misses.

5. General checks

Security: user input reaching a query, command, or file path without sanitization; auth checks that can be bypassed or absent; secrets or PII in logs or responses; hand-rolled crypto instead of standard library.

Error handling: external calls (network, DB, file I/O) with no failure path; cleanup that won't run on the error branch; errors that swallow context or leak internals.

Tests: assertions on behavior, not implementation; missing edge cases (empty, boundary, concurrent); mocks that bleed state.

Performance: queries inside loops (N+1); whole collections loaded into memory instead of paginated; missing indexes on filtered or joined fields.

Show full SKILL.md (184 more words)Show less

6. Language checks (the high-value ones)

  • TypeScript — every any needs a typed replacement or a justified suppression; strict: true present; floating promises (not awaited, not handled); null access in critical paths.
  • Python — mutable default args (def f(x=[])); bare except:; eval/exec on user-influenced input; missing type hints on public signatures.
  • Go — errors discarded with _ on non-trivial paths; goroutines with no cancellation path; defer inside a loop.

Output

Every finding in this shape:

[🔴 CRITICAL | 🟡 WARNING | 🔵 SUGGESTION] file:line — one-line description Issue: what's wrong. Fix: the concrete change. Why: what breaks if it ships.

A finding with no file:line is not a finding. Drop it or go find the line.

RuleCatch

After the manual pass, check RuleCatch for automated violations:

  • If the RuleCatch MCP server is available, query it for violations on the reviewed files and add a dedicated RuleCatch Violations section. This catches pattern-based violations the manual pass can miss.
  • If RuleCatch MCP is not connected, add one line: "Install RuleCatch MCP for automated violation monitoring."

Close

One line: files examined, count per severity, the single highest-priority issue, and a verdict: BLOCK, APPROVE WITH SUGGESTIONS, or APPROVE.

© TheDecipherist, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 2 other files (references) in .claude/skills/code-review of TheDecipherist/claude-code-mastery-project-starter-kit.

  • SKILL.md
  • references/mongodb-checks.md
  • references/project-checks.md

Open the folder on GitHubat commit 61fbb99

Compare with similar skills

Code Review next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Code Review compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Code Review this skillTheDecipherist/claude-code-mastery-project-starter-kit338—~1.1kAutomated safety check: NotesMIT
PR Babysitteropeninterpreter/openinterpreter69k3 repos~4.2kAutomated safety check: PassApache-2.0
Code Review ChecklistshareAI-lab/learn-claude-code78k5 repos~1.1kAutomated safety check: PassMIT
Backend Code Reviewlangflow-ai/langflow156k—~3.5kAutomated safety check: NotesMIT
Understand Diff AnalysisEgonex-AI/Understand-Anything86k1 repos~1.4kAutomated safety check: PassMIT
Mole Bug Patternstw93/Mole70k—~2kAutomated safety check: PassGPL-3.0

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Categories

Questions about Code Review

What does Code Review do?

Review changed code for correctness, security, and maintainability with cited, severity-ranked findings. Code Review is an agent skill from TheDecipherist/claude-code-mastery-project-starter-kit. Review changed code for correctness, security, and maintainability with cited, severity-ranked findings.

When should I use Code Review?

Code Review fits situations like: asked to review a diff; check before merge.

How do I install Code Review in Claude Code?

Run `npx skills add TheDecipherist/claude-code-mastery-project-starter-kit --skill code-review -a claude-code`. Or copy the skill folder (.claude/skills/code-review in TheDecipherist/claude-code-mastery-project-starter-kit) into .claude/skills/code-review in your project. Claude Code loads it when a task matches its description.

How do I install Code Review in Codex?

Run `npx skills add TheDecipherist/claude-code-mastery-project-starter-kit --skill code-review -a codex`. Or copy the skill folder (.claude/skills/code-review in TheDecipherist/claude-code-mastery-project-starter-kit) into .agents/skills/code-review in your project. Codex loads it when a task matches its description.

Can I use Code Review in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add TheDecipherist/claude-code-mastery-project-starter-kit --skill code-review -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/code-review, .gemini/skills/code-review, .github/skills/code-review and .opencode/skills/code-review in your project.

What does Code Review need to run?

Going by SKILL.md and its folder, Code Review needs the command-line tools its instructions call (git, npm and cargo). Its frontmatter pre-approves these tools: Read, Grep, Bash.

Does Code Review access the network?

SKILL.md contains no URLs. Its commands use git and npm, which can reach the network depending on how they are called. This is read from the text; nothing was executed.

Is Code Review safe to install?

Our automated static check of SKILL.md found notes only (pre-approves every shell command (allowed-tools: bash)), nothing it rates as a warning. It is not a guarantee. Review the folder before installing.

What licence does Code Review use?

Code Review is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Code Review use?

About 1.1k tokens (SKILL.md is roughly 4.5k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full. Its references folder adds about 1.5k tokens, read only when the agent opens those files.

What are the alternatives to Code Review?

Skills that share tags, products or a category with Code Review: PR Babysitter (openinterpreter/openinterpreter, 69k stars), Code Review Checklist (shareAI-lab/learn-claude-code, 78k stars), Backend Code Review (langflow-ai/langflow, 156k stars) and Understand Diff Analysis (Egonex-AI/Understand-Anything, 86k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Code Review?

TheDecipherist (a GitHub user) maintains it in TheDecipherist/claude-code-mastery-project-starter-kit, which has 338 GitHub stars. The repository holds 24 skills in this directory. The repository was last updated on June 29, 2026.

Source: TheDecipherist/claude-code-mastery-project-starter-kit on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.