formal-modeling

formal-modeling is a skill for Claude Code, Codex from in8finity/claude-plugin. It costs 142 tokens per session (17,070 once invoked), scanned A, original, no licence file.

A tool for writing, running, and understanding Alloy 6 models. Alloy is a language for describing systems and checking whether their rules and relationships hold.

In plain words
What is it for?
Use it to check state machines, business processes, data rules, API contracts, integrations, permissions, and workflows.
Why use it?
It helps reveal contradictions and edge cases in system rules before they become implementation bugs.

Skill for Claude CodeCodex

Part of the formal-methods plugin — 4 skills shipped together

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/in8finity/claude-plugin/formal-modeling
Any agent
npx skills add in8finity/claude-plugin --skill formal-modeling
Clone the repo
git clone --depth 1 https://github.com/in8finity/claude-plugin

Made for: Claude Code, Codex.

Or install formal-methods, the plugin that ships this one along with the rest of its 4 skills.

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-modeling

README.md
[![agentmods](https://agentmods.dev/badge/skills/in8finity/claude-plugin/formal-modeling.svg)](https://agentmods.dev/skills/in8finity/claude-plugin/formal-modeling)
Your own site
<a href="https://agentmods.dev/skills/in8finity/claude-plugin/formal-modeling"><img src="https://agentmods.dev/badge/skills/in8finity/claude-plugin/formal-modeling.svg" alt="Measured on agentmods" height="20"></a>
Per session 142 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 17,070 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 $0.00142 $0.17070
Opus 5 $0.00071 $0.08535
Sonnet 5 $0.00028 $0.03414
Haiku 4.5 $0.00014 $0.01707

Measured 3d ago against content hash adeac9935157, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

formal-modeling 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 3d ago.

The scan reads SKILL.md. This mod also ships 19 executable files (scripts/alloy_format.py, scripts/alloy_run.sh, scripts/check_enforcement.py, …), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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** and **python3** must be available
skills/formal-modeling/SKILL.md · 1,194 lines

The source is not reproduced here

No licence file

A repository with no LICENSE is all rights reserved by default, so the body is not copied here. The metadata, the measurements and the link are.

Read it on GitHub

Files

What ships with it

46 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. 3d ago First seen · 1,194 lines · 142 tokens per session scan A adeac9935157

Subscribe to this mod's changes

formal-modeling is a skill published in the GitHub repository in8finity/claude-plugin (2 stars, last pushed 3mo ago), with no licence file. It adds 142 tokens to every session and 17,070 once invoked, about $0.0007 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 2026-08-31.

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