FirstPrinciples

FirstPrinciples is a skill for Claude Code, Codex from DorShaer/Husk. It costs 91 tokens per session (1,587 once invoked), scanned A, original, no licence file.

A problem-solving method that breaks a situation down into basic facts, limits, and assumptions, then builds a solution from those foundations.

In plain words
What is it for?
Use it to examine difficult technical, product, or engineering problems and find solutions based on fundamental constraints.
Why use it?
It helps separate what must be true from guesses and preferences, so decisions are not based on untested assumptions.

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/dorshaer/husk/firstprinciples
Any agent
npx skills add DorShaer/Husk --skill firstprinciples
Clone the repo
git clone --depth 1 https://github.com/DorShaer/Husk

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 FirstPrinciples

README.md
[![agentmods](https://agentmods.dev/badge/skills/dorshaer/husk/firstprinciples.svg)](https://agentmods.dev/skills/dorshaer/husk/firstprinciples)
Your own site
<a href="https://agentmods.dev/skills/dorshaer/husk/firstprinciples"><img src="https://agentmods.dev/badge/skills/dorshaer/husk/firstprinciples.svg" alt="Measured on agentmods" height="20"></a>
Per session 91 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,587 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. Scan, not verified.
Origin unknown 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 $0.00091 $0.01587
Opus 5 $0.00046 $0.00794
Sonnet 5 $0.00018 $0.00317
Haiku 4.5 $0.00009 $0.00159

Measured 5d ago against content hash 4aaba3d1ddd5, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

FirstPrinciples scanned grade A with 1 finding 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 5d 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.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

curl -s -X POST http://localhost:31337/notify \
libs/lifeos/skills/FirstPrinciples/SKILL.md · 153 lines

The source is not reproduced here

A licence we could not identify

The repository carries a LICENSE file, but it is custom or dual enough that GitHub cannot name it and neither can this catalogue. Unknown terms are not permission, so the body is not copied here. Read the licence at the source and decide for yourself.

Read it on GitHub

Files

What ships with it

3 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. 5d ago First seen · 153 lines · 91 tokens per session scan A 4aaba3d1ddd5

Subscribe to this mod's changes

FirstPrinciples is a skill published in the GitHub repository DorShaer/Husk (12 stars, last pushed yesterday), with no licence file. It adds 91 tokens to every session and 1,587 once invoked, about $0.0005 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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