python-design

A set of Python design guidelines for command-line scripts and utilities. It focuses on type-first code, module structure, managing complexity, and recognizing design problems.

In plain words
What is it for?
Use it when reading, writing, reviewing, refactoring, or planning Python CLI scripts and utilities, including files under .cstl/scripts/.
Why use it?
It helps keep small Python tools understandable and maintainable as they gain options, responsibilities, and dependencies.

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/blxzer77/cursor-trellis/python-design
Any agent
npx skills add blxzer77/cursor-trellis --skill python-design
Clone the repo
git clone --depth 1 https://github.com/blxzer77/cursor-trellis

Made for: Claude Code, Codex.

Per session 74 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,550 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 $0.00074 $0.03550
Opus 5 $0.00037 $0.01775
Sonnet 5 $0.00015 $0.00710
Haiku 4.5 $0.00007 $0.00355

Measured yesterday against content hash a4276ca55fa6, 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 yesterday.

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. yesterday First seen · 452 lines · 74 tokens per session scan A a4276ca55fa6

Subscribe to this mod's changes

python-design is a skill published in the GitHub repository blxzer77/cursor-trellis (15 stars, last pushed 3d ago), licensed AGPL-3.0. It adds 74 tokens to every session and 3,550 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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