python-core

python-core is a skill for Claude Code, Codex from adonai-labs/agent-runway. It costs 76 tokens per session (650 once invoked), scanned A, original, MIT.

Python implementation guidance for backend services and APIs, covering project structure, testing, security, and production monitoring.

In plain words
What is it for?
Use it to structure Python applications, design backend services or APIs, write tests with pytest, handle security concerns, and add operational visibility.
Why use it?
It helps developers make Python services easier to maintain, test, secure, and operate reliably.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one. Also seen: mentions Claude Code.

Good fit Use it to structure Python applications, design backend services or APIs, write tests with pytest, handle security concerns, and add operational visibility.

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Install with agentmods
npx agentmods add skills/adonai-labs/agent-runway/skill-python-core
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 adonai-labs/agent-runway --skill skill-python-core
Clone the repo
git clone --depth 1 https://github.com/adonai-labs/agent-runway

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-core

README.md
[![agentmods](https://agentmods.dev/badge/skills/adonai-labs/agent-runway/skill-python-core.svg)](https://agentmods.dev/skills/adonai-labs/agent-runway/skill-python-core)
Your own site
<a href="https://agentmods.dev/skills/adonai-labs/agent-runway/skill-python-core"><img src="https://agentmods.dev/badge/skills/adonai-labs/agent-runway/skill-python-core.svg" alt="Measured on agentmods" height="20"></a>
Per session 76 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 650 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 original 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 $0.00076 $0.00650
Opus 5 $0.00038 $0.00325
Sonnet 5 $0.00015 $0.00130
Haiku 4.5 $0.00008 $0.00065

Measured 4d ago against content hash 6fc717125cff, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-07, from the pricing page.

Security

Grade A, and why

python-core 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 4d 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.

src/stacks/python/skill-python-core/SKILL.md · 66 lines

How it starts

The opening of the file, as written. The whole thing — 66 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Python Core

How to invoke

After agent-runway add python, the skill is installed at .cursor/skills/python-core/. Use:

  • Cursor: @python-core or ask a Python question while editing *.py (rules auto-attach)
  • Claude Code: reference .agent-runway/skills/python-core/SKILL.md or ask in context of Python files

Examples:

  • How should I structure this FastAPI service?
  • How do I test this use case without hitting the database?
  • How do I add structured logging with correlation IDs?
  • Is this error handling idiomatic Python?

Not sure which skill to use? Start with /start — it classifies intent and routes to the right skill.


Guiding principles

Simplicity first. Python's culture favours readability and directness — respect it.

  • Start flat; add structure only when complexity demands it
  • One function, one responsibility — small, testable, named for what it does
  • SOLID applies: DIP via dependency injection, ISP via focused ABCs, DRY for business logic
  • Prefer explicit over magic; avoid metaclasses, deep decorators, and framework-specific tricks unless necessary
  • Clean Architecture at the right scale — do not introduce it for a script or a small API

What this skill helps with

  • Project structure scaled to complexity — scripts to full layered services
  • FastAPI / Django REST / Flask patterns — routing, validation, error handling
  • Testing: pytest, fixtures, mocking, integration with Testcontainers
  • Security: input validation, SQL injection, secrets, dependency audit
  • Observability: structlog / standard logging, OpenTelemetry, health endpoints
  • Toolchain: pyproject.toml, uv, type checking with mypy/pyright

Skill files

File Contents
architecture.md Project structure, layers, dependency rules, config
patterns.md Service layer, repository, dependency injection, error handling
testing.md pytest setup, fixtures, mocking, Testcontainers, API testing
security.md Input validation, SQL injection, secrets, subprocess safety
observability.md Structured logging, OpenTelemetry, health checks
reference.md Toolchain, pyproject.toml, common commands

Read the full file on GitHub · 66 lines

Files

What ships with it

6 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. 4d ago First seen · 66 lines · 76 tokens per session scan A 6fc717125cff

Subscribe to this mod's changes

python-core is a skill published in the GitHub repository adonai-labs/agent-runway (2 stars, last pushed 17d ago), licensed MIT. It adds 76 tokens to every session and 650 once invoked, about $0.0004 per session on Opus 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 2026-09-03.