think-five-whys

think-five-whys is a skill for Claude Code from product-on-purpose/thinking-framework-skills. It costs 94 tokens per session (1,686 once invoked), scanned A, original, Apache-2.0.

A root-cause exercise that asks “why?” repeatedly to build a single chain from a problem toward a cause, while checking at each step whether several causes may be involved.

In plain words
What is it for?
Use it when Five Whys is specifically requested to investigate failures, defects, incidents, or recurring problems and identify a possible countermeasure for the final cause.
Why use it?
It gives a simple way to investigate a problem but avoids presenting one guessed cause as the whole explanation. When the problem has multiple causes, it signals that a broader breakdown is needed.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin.

Part of the thinking-framework-skills plugin — 68 skills, 10 commands, 1 agent shipped together

Good fit Use it when Five Whys is specifically requested to investigate failures, defects, incidents, or recurring problems and identify a possible countermeasure for the final cause.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/product-on-purpose/thinking-framework-skills/think-five-whys
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.

Any agent
npx skills add product-on-purpose/thinking-framework-skills --skill think-five-whys
Clone the repo
git clone --depth 1 https://github.com/product-on-purpose/thinking-framework-skills

Made for: Claude Code.

Or install thinking-framework-skills, the plugin that ships this one along with the rest of its 68 skills, 10 commands, 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 think-five-whys

README.md
[![agentmods](https://agentmods.dev/badge/skills/product-on-purpose/thinking-framework-skills/think-five-whys/github.svg)](https://agentmods.dev/skills/product-on-purpose/thinking-framework-skills/think-five-whys)
Your own site
<a href="https://agentmods.dev/skills/product-on-purpose/thinking-framework-skills/think-five-whys"><img src="https://agentmods.dev/badge/skills/product-on-purpose/thinking-framework-skills/think-five-whys/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 think-five-whys

Your own site · 80×15
<a href="https://agentmods.dev/skills/product-on-purpose/thinking-framework-skills/think-five-whys"><img src="https://agentmods.dev/badge/skills/product-on-purpose/thinking-framework-skills/think-five-whys.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 94 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,686 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 $0.00094 $0.01686
Opus 5 $0.00047 $0.00843
Sonnet 5 $0.00019 $0.00337
Haiku 4.5 $0.00009 $0.00169

Measured 12d ago against content hash 033ee19ef2d6, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade A, and why

think-five-whys 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 12d 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/think-five-whys/SKILL.md · 72 lines

How it starts

The opening of the file, as written. The whole thing — 72 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Five Whys

Five Whys traces a problem to a root cause by asking "why?" of each answer, about five times, until you reach a cause worth fixing. It is famous and frequently requested, and its evidence is weak: the critical literature finds it flattens multi-cause problems into a single chain and discards the rest. This skill runs Five Whys honestly. It leads with that caveat, then forces the one discipline a bare why-chain omits and that makes it safe to run at all: at each step, flag whether more than one cause could apply, and the moment the problem is multi-cause, say so and hand it to think-issue-tree. The output is a single linear why-chain with a branch-or-not flag on each step plus one countermeasure aimed at the terminal node, not a confident single root cause presented as the cause.

Before you run this: the evidence caveat

Five Whys is tier X (weak or contradictory evidence). The governing critique is Alan J. Card, "The problem with '5 whys'," BMJ Quality & Safety 26(8) (2017): 671-677, which argues the technique oversimplifies complex problems, follows a single causal chain when failures are multi-causal, and limits understanding of how processes actually fail; Card's prescription is to move to branching, systems-oriented causal-tree diagramming. John Allspaw, "The Infinite Hows (or, the Dangers of the Five Whys)" (2014), adds that in socio-technical systems the linear "why" chain drifts toward a person and a counterfactual (the "Bad Apple" blame trap) and recommends "how" over "why" to recover the multi-contributor picture. The method is reliable only for simple, linear, single-cause failures; beyond them its output looks like THE cause when it is one cause among many.

So a single chain is not a verdict. If you run Five Whys here, the value is not the chain, it is the discipline this skill adds: flagging at every step whether more than one cause could apply, and stopping to redirect when it can. For any problem that might have more than one cause - which is most real problems - think-issue-tree is the stronger move: it branches with MECE-plus-remainder discipline instead of forcing one path. Do not report a single root cause as the answer to a many-cause problem, and do not invent quantified claims about Five Whys' effectiveness (none are supported).

Read the full file on GitHub · 72 lines

Files

What ships with it

5 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. 12d ago First seen · 72 lines · 94 tokens per session scan A 033ee19ef2d6

Subscribe to this mod's changes

think-five-whys is a skill published in the GitHub repository product-on-purpose/thinking-framework-skills (15 stars, last pushed today), licensed Apache-2.0. It adds 94 tokens to every session and 1,686 once invoked, about $0.0005 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.