What is first-principles-thinking?

A reasoning skill for breaking a problem down into basic facts and assumptions before choosing an approach. It can be used across different technical or non-technical domains.

It is for examining whether an approach is right, challenging assumptions, analyzing a design from scratch, and looking for alternatives based on fundamental constraints.

It helps question inherited designs and explanations instead of accepting a process simply because it is familiar.

How blxzer77/cursor-trellis configures Claude Code and Codex

Reuse

Borrowing it

Nothing to install: this file belongs to blxzer77/cursor-trellis. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file

curl -O https://raw.githubusercontent.com/blxzer77/cursor-trellis/main/.agents/skills/first-principles-thinking/SKILL.md

Clone the repo

git clone --depth 1 https://github.com/blxzer77/cursor-trellis

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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/blxzer77/cursor-trellis/first-principles-thinking/github.svg)](https://agentmods.dev/skills/blxzer77/cursor-trellis/first-principles-thinking)

Your own site

<a href="https://agentmods.dev/skills/blxzer77/cursor-trellis/first-principles-thinking"><img src="https://agentmods.dev/badge/skills/blxzer77/cursor-trellis/first-principles-thinking/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.

Your own site · 80×15

<a href="https://agentmods.dev/skills/blxzer77/cursor-trellis/first-principles-thinking"><img src="https://agentmods.dev/badge/skills/blxzer77/cursor-trellis/first-principles-thinking.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 164 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 4,013 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 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.

Model	Per session	Once invoked
Fable 5.1	$0.00164	$0.04013
Opus 5.5	$0.00066	$0.01605
Sonnet 5.5	$0.00033	$0.00803
Haiku 4.5	$0.00016	$0.00401

Measured 2mo ago against content hash 756abbb8da77, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

first-principles-thinking 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 2mo 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.

.agents/skills/first-principles-thinking/SKILL.md · 404 lines

The source is not reproduced here

Licensed AGPL-3.0

The repository is licensed AGPL-3.0, which this catalogue does not treat as permission to reproduce the file. Read it at the source.

Read it on GitHub

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.

2mo ago First seen · 404 lines · 164 tokens per session scan A 756abbb8da77

Subscribe to this mod's changes

first-principles-thinking is a skill published in the GitHub repository blxzer77/cursor-trellis (18 stars, last pushed 1mo ago), licensed AGPL-3.0. It adds 164 tokens to every session and 4,013 once invoked, about $0.0007 per session on Opus 5.5. 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.

Planning

first-principles-thinking next to 6 skills from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
first-principles-thinkingblxzer77/cursor-trellis	Skill	18	1mo ago	AGPL-3.0	A	164	Claude Code, Codex
imagegenopenai/codex	Skill	133k	yesterday	Apache-2.0	A	113	Codex
playwright-climicrosoft/playwright	Skill	99k	yesterday	Apache-2.0	A	19	Claude Code
local-ai-agentsmicrosoft/ai-agents-for-beginners	Skill	79k	4d ago	MIT	A	200	Claude Code, Codex
systematic-debuggingobra/superpowers	Skill	313k	3d ago	MIT	A	21	Claude Code
next-cache-components-adoptionvercel/next.js	Skill	143k	yesterday	MIT	A	95	Claude Code
next-partial-prefetching-adoptionvercel/next.js	Skill	143k	yesterday	MIT	A	103	Claude Code

cursor-trellis: Skill for Claude Code