python-design

python-design is a skill for Claude Code, Codex from LonelyHerbivore/Trellis-Herbivore. It costs 73 tokens per session (3,549 once invoked), scanned A, original, AGPL-3.0.

A set of design guidelines for Python command-line programs and utility scripts. It focuses on clear types, well-contained modules, managing complexity, and spotting warning signs in code.

In plain words
What is it for?
Use it when writing, reading, reviewing, refactoring, or planning Python CLI scripts and utilities, especially scripts in a .trellis directory.
Why use it?
It helps make scripts easier to understand, test, and change as they grow. It also provides criteria for reviewing or restructuring Python code.

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/lonelyherbivore/trellis-herbivore/python-design
Any agent
npx skills add LonelyHerbivore/Trellis-Herbivore --skill python-design
Clone the repo
git clone --depth 1 https://github.com/LonelyHerbivore/Trellis-Herbivore

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 python-design

README.md
[![agentmods](https://agentmods.dev/badge/skills/lonelyherbivore/trellis-herbivore/python-design.svg)](https://agentmods.dev/skills/lonelyherbivore/trellis-herbivore/python-design)
Your own site
<a href="https://agentmods.dev/skills/lonelyherbivore/trellis-herbivore/python-design"><img src="https://agentmods.dev/badge/skills/lonelyherbivore/trellis-herbivore/python-design.svg" alt="Measured on agentmods" height="20"></a>
Per session 73 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,549 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 $0.00073 $0.03549
Opus 5 $0.00036 $0.01775
Sonnet 5 $0.00015 $0.00710
Haiku 4.5 $0.00007 $0.00355

Measured 5d ago against content hash 6520ddaf474e, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

python-design 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.

Runs shell commandslowCapability

Expected in a hook, worth knowing in a rule or an instructions file.

def run_git(args: list[str]) -> subprocess.CompletedProcess:
.agents/skills/python-design/SKILL.md · 452 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

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 · 452 lines · 73 tokens per session scan A 6520ddaf474e

Subscribe to this mod's changes

python-design is a skill published in the GitHub repository LonelyHerbivore/Trellis-Herbivore (95 stars, last pushed 11d ago), licensed AGPL-3.0. It adds 73 tokens to every session and 3,549 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 1 finding (runs shell commands). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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