reviewing-code

reviewing-code is a skill for Claude Code, Codex from PrefectHQ/fastmcp. It costs 43 tokens per session (964 once invoked), scanned A, original, Apache-2.0.

Guidance for reviewing code changes for correctness, maintainability, quality, and fit with a project's goals. It focuses on specific, actionable feedback and checks whether dependency changes match the supported versions.

In plain words
What is it for?
Use it when reviewing pull requests or implementations, checking API design and coding patterns, assessing dependency compatibility, and explaining concrete fixes to contributors.
Why use it?
It helps reviewers reject changes that are unwanted or incompatible even when the code itself is well written.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/prefecthq/fastmcp/code-review
Any agent
npx skills add PrefectHQ/fastmcp --skill code-review
Clone the repo
git clone --depth 1 https://github.com/PrefectHQ/fastmcp

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for reviewing-code

README.md
[![agentmods](https://agentmods.dev/badge/skills/prefecthq/fastmcp/code-review.svg)](https://agentmods.dev/skills/prefecthq/fastmcp/code-review)
Your own site
<a href="https://agentmods.dev/skills/prefecthq/fastmcp/code-review"><img src="https://agentmods.dev/badge/skills/prefecthq/fastmcp/code-review.svg" alt="Measured on agentmods" height="20"></a>
Per session 43 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 964 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00043 $0.00964
Opus 5 $0.00022 $0.00482
Sonnet 5 $0.00009 $0.00193
Haiku 4.5 $0.00004 $0.00096

Measured 4d ago against content hash 5ae40fc0c173, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

reviewing-code scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 4d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.claude/skills/code-review/SKILL.md · 102 lines

How it starts

The opening of the file, as written. The whole thing — 102 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Code Review

Philosophy

Code review maintains a healthy codebase while helping contributors succeed. The burden of proof is on the PR to demonstrate it adds value. Your job is to help it get there through actionable feedback.

Critical: A perfectly written PR that adds unwanted functionality must still be rejected. The code must advance the codebase in the intended direction. When rejecting, provide clear guidance on how to align with project goals.

Be friendly and welcoming while maintaining high standards. Call out what works well. When code needs improvement, be specific about why and how to fix it.

What to Focus On

Does this advance the codebase correctly?

Even perfect code for unwanted features should be rejected.

Dependency version compatibility

When a PR adapts code to a new version of a dependency (e.g., removing a parameter that was dropped upstream, using a new API):

  • The version pin in pyproject.toml must match. If the change breaks compatibility with the previously-pinned minimum version, the minimum version must be bumped. Otherwise users on the old version get a regression.
  • If backwards compatibility with the old version is desired, the code must handle both versions (e.g., try/except, version check). Simply deleting the old API usage without bumping the pin is always wrong — it silently breaks users on the old version.
  • Lock file (uv.lock) changes should be scoped to the PR's purpose. A PR fixing a ty compatibility issue should not also include unrelated dependency version bumps (anthropic, google-auth, etc.) from running uv sync --upgrade. These create noise and make the diff harder to review.

API design and naming

Identify confusing patterns or non-idiomatic code:

  • Parameter values that contradict defaults
  • Mutable default arguments
  • Unclear naming that will confuse future readers
  • Inconsistent patterns with the rest of the codebase

Specific improvements

Provide actionable feedback, not generic observations.

Read the full file on GitHub · 102 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 4d ago First seen · 102 lines · 43 tokens per session scan A 5ae40fc0c173

Subscribe to this mod's changes

reviewing-code is a skill published in the GitHub repository PrefectHQ/fastmcp (27,510 stars, last pushed yesterday), licensed Apache-2.0. It adds 43 tokens to every session and 964 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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