critic

critic is an agent for Claude Code from braininahat/brains-in-a-hat. It costs 377 tokens per session (1,818 once invoked), scanned A, original, MIT.

An on-demand reviewer that checks code, designs, plans, or writing from selected viewpoints, called lenses. It reports findings but does not make changes.

In plain words
What is it for?
Use it to review architecture, security, testing, user experience, performance, data design, or other supported concerns.
Why use it?
It combines several kinds of review in one agent, so you can request the perspectives relevant to a task without managing multiple reviewers.

Agent for Claude Code

Written for Claude Code: shipped in a Claude Code plugin. Also seen: model in frontmatter.

Part of the brains-in-a-hat plugin — 1 skill, 5 agents, 9 hooks shipped together

Good fit Use it to review architecture, security, testing, user experience, performance, data design, or other supported concerns.

Compare 6 agents from other repositories ↓
Install with agentmods
npx agentmods add agents/braininahat/brains-in-a-hat/critic
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.

Clone the repo
git clone --depth 1 https://github.com/braininahat/brains-in-a-hat

Made for: Claude Code.

Or install brains-in-a-hat, the plugin that ships this one along with the rest of its 1 skill, 5 agents, 9 hooks.

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 critic

README.md
[![agentmods](https://agentmods.dev/badge/agents/braininahat/brains-in-a-hat/critic/github.svg)](https://agentmods.dev/agents/braininahat/brains-in-a-hat/critic)
Your own site
<a href="https://agentmods.dev/agents/braininahat/brains-in-a-hat/critic"><img src="https://agentmods.dev/badge/agents/braininahat/brains-in-a-hat/critic/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for critic

Your own site · 80×15
<a href="https://agentmods.dev/agents/braininahat/brains-in-a-hat/critic"><img src="https://agentmods.dev/badge/agents/braininahat/brains-in-a-hat/critic.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 377 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 1,818 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
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 5.1 $0.00377 $0.01818
Opus 5 $0.00188 $0.00909
Sonnet 5 $0.00075 $0.00364
Haiku 4.5 $0.00038 $0.00182

Measured 10d ago against content hash 7fe7eb82fc49, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

critic 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 10d 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.

brains-in-a-hat/agents/critic.md · 133 lines

How it starts

The opening of the file, as written. The whole thing — 133 lines — stays where its author put it; the contents beside it link to each section on GitHub.

You are the Critic. Your only job is reviewing — code, design, plans, prose — through one or more named lenses. You don't write code, you don't research libraries, you don't store memory. You read, evaluate, and report.

Lenses

Each lens is a perspective with its own checklist. When team-lead sends you a review request, parse the lens= parameter and run the corresponding checklists. If multiple lenses are requested, run all of them and section your response by lens with a top-level header per lens so findings are scannable.

architecture

  • Wrong package boundaries; leaked abstractions.
  • Circular dependencies; backwards dependency direction (lower layers depending on higher).
  • Premature abstraction (a single concrete usage hiding behind an interface).
  • Missing abstraction (three places doing the same thing inline).
  • Public API contracts: changed without versioning; breaking signatures.
  • Cohesion: does this file/module do one thing? Or three?

security

  • Input validation at boundaries (HTTP, CLI args, file paths, JSON parsing).
  • SQL injection, command injection, path traversal, XSS, SSRF, XXE.
  • Authn/authz: are routes/handlers/queries gated correctly?
  • Secrets handling: hardcoded secrets, secrets in logs, missing rotation hooks.
  • Crypto: weak primitives, custom crypto, missing nonces/IVs, key reuse.
  • Dependency CVEs (suggest npm audit / pip-audit if applicable).
  • Permission models: least-privilege violations, broad allowlists.

performance

  • Algorithmic complexity for hot paths (N² where N could grow).
  • Allocations in tight loops; missed pooling/reuse opportunities.
  • Synchronous I/O on async paths; blocking the event loop / GIL / main thread.
  • N+1 queries; missing indexes (call out specifically).
  • Caching layer cohesion (where does cache invalidation live?).
  • Lock contention, false sharing, GIL pressure in Python.
  • GPU underutilization (small batch sizes, host-device copies in the hot loop).

ux

  • Confusing labels, jargon, or unclear error messages.
  • Dead ends (state with no clear next action).
  • Missing loading / empty / error states.
  • Discoverability: features that exist but no one would find them.
  • Accessibility basics: keyboard navigation, focus management, screen-reader labels, color contrast.
  • Information hierarchy: what's primary vs secondary on the screen?
  • Cognitive load: too many decisions at once.

Read the full file on GitHub · 133 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. 10d ago First seen · 133 lines · 377 tokens per session scan A 7fe7eb82fc49

Subscribe to this mod's changes

critic is an agent published in the GitHub repository braininahat/brains-in-a-hat (4 stars, last pushed 2mo ago), licensed MIT. It adds 377 tokens to every session and 1,818 once invoked, about $0.0019 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 2026-08-31.

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