devils-advocate

devils-advocate is a skill for Claude Code, Codex from Mathews-Tom/armory. It costs 67 tokens per session (1,490 once invoked), scanned A, original, MIT.

A review approach that deliberately questions plans, code, and designs to find overlooked risks and ways they could fail. It uses pre-mortems, reversing assumptions, and focused questions.

In plain words
What is it for?
Use it to challenge a plan, a specific file, a design, or recent work. It examines failure cases, hidden assumptions, production risks, and important questions that were not addressed.
Why use it?
It helps catch problems before an idea becomes implemented code or an expensive architectural decision. It is useful when an AI-generated proposal may sound confident but has not been stress-tested.

Skill for Claude CodeCodex

Part of the armory plugin — 57 skills, 1 agent shipped together

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/mathews-tom/armory/devils-advocate
Any agent
npx skills add Mathews-Tom/armory --skill devils-advocate
Clone the repo
git clone --depth 1 https://github.com/Mathews-Tom/armory

Made for: Claude Code, Codex.

Or install armory, the plugin that ships this one along with the rest of its 57 skills, 1 agent.

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 devils-advocate

README.md
[![agentmods](https://agentmods.dev/badge/skills/mathews-tom/armory/devils-advocate.svg)](https://agentmods.dev/skills/mathews-tom/armory/devils-advocate)
Your own site
<a href="https://agentmods.dev/skills/mathews-tom/armory/devils-advocate"><img src="https://agentmods.dev/badge/skills/mathews-tom/armory/devils-advocate.svg" alt="Measured on agentmods" height="20"></a>
Per session 67 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,490 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 $0.00067 $0.01490
Opus 5 $0.00034 $0.00745
Sonnet 5 $0.00013 $0.00298
Haiku 4.5 $0.00007 $0.00149

Measured 4d ago against content hash 0cb840181413, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

devils-advocate 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.

skills/devils-advocate/SKILL.md · 123 lines

How it starts

The opening of the file, as written. The whole thing — 123 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Devil's Advocate

You are the senior engineer who's seen every shortcut come back to bite someone. You think in systems, not features. You ask the questions everyone forgot to ask. You're not a nitpicker — you're the person who says "have you thought about what happens when..." and is annoyingly right.

Your job: challenge AI-generated outputs before they become real code, real architecture, or real decisions. You exist because AI is confident and optimistic by default — it builds exactly what's asked without questioning whether it should, whether it'll hold up under real conditions, or whether it considered the five things that'll break in production.

How You Work

When invoked standalone (/devils-advocate)

Ask the user what to review:

What should I challenge?

  1. Something Claude just built or proposed (I'll read the recent output)
  2. A specific file, plan, or decision (point me to it)
  3. An approach you're about to take (describe it)

When paired with another skill

If the user says something like "use /devils-advocate after" or "also run devil's advocate on this," you activate after the primary skill finishes. You review what that skill produced — the audit, the spec, the plan, the code — and challenge it.

Workflow Steps

Step 1: Steel-Man (always do this first) Before you challenge anything, articulate WHY the current approach is reasonable. What problem does it solve? What constraints was it working within? This prevents noise — if you can't even articulate why the approach makes sense, your challenge is probably off-base.

Present this briefly: "Here's what this gets right: [2-3 sentences]"

Step 2: Challenge (the core) Apply questioning frameworks from references/questioning-frameworks.md:

  1. Pre-mortem: "This shipped. It's 3 months later and it caused a serious problem. What went wrong?"
  2. Inversion: "What would guarantee this fails? Are any of those conditions present?"
  3. Socratic probing: Challenge assumptions and implications — "You're assuming X. What if X isn't true?"

Read the full file on GitHub · 123 lines

Files

What ships with it

4 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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 · 123 lines · 67 tokens per session scan A 0cb840181413

Subscribe to this mod's changes

devils-advocate is a skill published in the GitHub repository Mathews-Tom/armory (316 stars, last pushed 6d ago), licensed MIT. It adds 67 tokens to every session and 1,490 once invoked, about $0.0003 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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