C31-1st

C31-1st is a skill for Claude Code, Codex from ChianW/C31. It costs 102 tokens per session (949 once invoked), scanned A, original, MIT.

A first-principles thinking framework. First-principles thinking breaks a problem down to basic facts and rebuilds the solution from those facts instead of copying familiar approaches.

In plain words
What is it for?
Analyzing questions such as why something works, finding the essential parts of a problem, and deriving a solution from fundamental facts. It can respond in the user's conversation language.
Why use it?
It helps examine the underlying reason for a problem before choosing an implementation, rather than making small changes based only on precedent.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit Analyzing questions such as why something works, finding the essential parts of a problem, and deriving a solution from fundamental facts. It can respond in the user's conversation language.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/chianw/c31/c31-1st
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 ChianW/C31 --skill c31-1st
Clone the repo
git clone --depth 1 https://github.com/ChianW/C31

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 C31-1st

README.md
[![agentmods](https://agentmods.dev/badge/skills/chianw/c31/c31-1st.svg)](https://agentmods.dev/skills/chianw/c31/c31-1st)
Your own site
<a href="https://agentmods.dev/skills/chianw/c31/c31-1st"><img src="https://agentmods.dev/badge/skills/chianw/c31/c31-1st.svg" alt="Measured on agentmods" height="20"></a>
Per session 102 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 949 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 $0.00102 $0.00949
Opus 5 $0.00051 $0.00475
Sonnet 5 $0.00020 $0.00190
Haiku 4.5 $0.00010 $0.00095

Measured 8d ago against content hash 15c8ef7e0ab1, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-08, from the pricing page.

Security

Grade A, and why

C31-1st 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 8d 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/core/C31-1st/SKILL.md · 84 lines

How it starts

The opening of the file, as written. The whole thing — 84 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Multilingual Triggers

Language Trigger phrases
EN C31-1st
ZH 第一性原理, 追本溯源, 本质
JA 第一原理, 本質を探る

Output language: Respond automatically in the user's conversation language.

First Principle Thinking

Trace back to the root, redefine — do not merely optimize.

Core Definition

First Principles Thinking is a method of breaking down complex things to the most fundamental physical or axiomatic facts, and then rebuilding solutions from those "ground truths" — rather than relying on analogy or imitating convention.

Analogical Thinking vs. First Principles

Dimension Analogical Thinking (conventional) First Principles (ground-up innovation)
Starting point Follow past experience, industry norms, or what others did Strip away surface appearances and target the irreducible essential elements
Reasoning method Inductive: others succeeded this way, so I'll do the same Deductive: derive new solutions from fundamental laws and objective facts
End result Incremental improvements and fine-tuning (optimizing what exists) Innovative breakthroughs and reconstruction (redefining what exists)

Classic Case: Elon Musk and SpaceX

Conventional thinking (analogical):

"Spacecraft have always been expensive — that's been true for decades. Buying a ready-made rocket is too costly, so lowering launch costs seems impossible."

First Principles:

"What are the core materials in a rocket? Aluminum, titanium, copper, carbon fiber. These raw materials are actually quite cheap on commodity markets — roughly 2% of the rocket's total price. So instead of buying finished products, we buy the raw materials and build it ourselves from scratch."

Result: Launch costs dropped to one-tenth or even one-hundredth of the original.

Practice Steps

When executing First Principles thinking, strictly follow these three steps:

Read the full file on GitHub · 84 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. 8d ago First seen · 84 lines · 102 tokens per session scan A 15c8ef7e0ab1

Subscribe to this mod's changes

C31-1st is a skill published in the GitHub repository ChianW/C31 (1 stars, last pushed 13d ago), licensed MIT. It adds 102 tokens to every session and 949 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 2026-08-31.

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