formal-logic

formal-logic is a skill for Claude Code, Codex from xjtulyc/awesome-rosetta-skills. It costs 41 tokens per session (5,165 once invoked), scanned C, original, no licence file.

A toolkit for expressing logical statements as computer-checkable problems and proofs. It works with Z3, a constraint solver, SAT problems, modal logic, and Lean 4 proof verification.

In plain words
What is it for?
Use it to encode propositional and first-order logic, solve SAT and SMT constraints, analyse S5 modal logic, and verify proofs in Lean 4.
Why use it?
It helps check whether logical arguments are consistent, satisfiable, or formally proven instead of relying only on manual inspection. It also provides ways to encode complex reasoning for automated checking.

Skill for Claude CodeCodex

Which agent this was written for is unclear — body not stored (licence); the path alone says nothing.

Good fit Use it to encode propositional and first-order logic, solve SAT and SMT constraints, analyse S5 modal logic, and verify proofs in Lean 4.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/xjtulyc/awesome-rosetta-skills/formal-logic
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 xjtulyc/awesome-rosetta-skills --skill formal-logic
Clone the repo
git clone --depth 1 https://github.com/xjtulyc/awesome-rosetta-skills

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 formal-logic

README.md
[![agentmods](https://agentmods.dev/badge/skills/xjtulyc/awesome-rosetta-skills/formal-logic/github.svg)](https://agentmods.dev/skills/xjtulyc/awesome-rosetta-skills/formal-logic)
Your own site
<a href="https://agentmods.dev/skills/xjtulyc/awesome-rosetta-skills/formal-logic"><img src="https://agentmods.dev/badge/skills/xjtulyc/awesome-rosetta-skills/formal-logic/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 formal-logic

Your own site · 80×15
<a href="https://agentmods.dev/skills/xjtulyc/awesome-rosetta-skills/formal-logic"><img src="https://agentmods.dev/badge/skills/xjtulyc/awesome-rosetta-skills/formal-logic.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 41 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 5,165 The whole file, excluding the scripts and references it only reads on demand.
Security scan C 2 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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00041 $0.05165
Opus 5 $0.00020 $0.02583
Sonnet 5 $0.00008 $0.01033
Haiku 4.5 $0.00004 $0.00517

Measured 8d ago against content hash e12dfe88e70d, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade C, and why

formal-logic scanned grade C with 2 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.

Downloads and executes remote codehighSupply chain

curl | sh runs whatever the server returns today, which is not necessarily what it returned when this was reviewed.

# curl https://raw.githubusercontent.com/leanprover/elan/master/elan-init.sh -sSf | sh

Makes network callslowCapability

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

# curl https://raw.githubusercontent.com/leanprover/elan/master/elan-init.sh -sSf | sh
skills/14-philosophy/formal-logic/SKILL.md · 569 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

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 · 569 lines · 41 tokens per session scan C e12dfe88e70d

Subscribe to this mod's changes

formal-logic is a skill published in the GitHub repository xjtulyc/awesome-rosetta-skills (34 stars, last pushed 5mo ago), with no licence file. It adds 41 tokens to every session and 5,165 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it C with 2 findings (downloads and executes remote code, makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.

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