What is devs:python-core?

A reference hub for writing, debugging, reviewing, and designing Python software, including typing, asynchronous code, testing, FastAPI, dependencies, and packaging.

Use it for Python tracebacks, mypy errors, asyncio work, pytest tests, FastAPI services, uv dependency management, and new-project scaffolding.

It gives developers verified guidance for common Python problems instead of making assumptions about library versions or project setup.

devs:python-core — Skill for Claude Code by aaronbassett/agent-foundry

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 aaronbassett/agent-foundry --skill python-core

Clone the repo

git clone --depth 1 https://github.com/aaronbassett/agent-foundry

Made for: Claude Code.

Or install devs, the plugin that ships this one along with the rest of its 8 skills, 1 command, 7 agents.

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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/aaronbassett/agent-foundry/python-core/github.svg)](https://agentmods.dev/skills/aaronbassett/agent-foundry/python-core)

Your own site

<a href="https://agentmods.dev/skills/aaronbassett/agent-foundry/python-core"><img src="https://agentmods.dev/badge/skills/aaronbassett/agent-foundry/python-core/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.

Your own site · 80×15

<a href="https://agentmods.dev/skills/aaronbassett/agent-foundry/python-core"><img src="https://agentmods.dev/badge/skills/aaronbassett/agent-foundry/python-core.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 78 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 826 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 1 finding. 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.

Model	Per session	Once invoked
Fable 5.1	$0.00078	$0.00826
Opus 5.5	$0.00031	$0.00330
Sonnet 5.5	$0.00016	$0.00165
Haiku 4.5	$0.00008	$0.00083

Measured 1mo ago against content hash d47ceb4e370c, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

devs:python-core 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 1mo ago.

The scan reads SKILL.md. This mod also ships 3 executable files (scripts/audit_dependencies.sh, scripts/init_python_project.sh, scripts/setup_logging.sh), 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.

Reference hub for Python work. Verify versions and APIs against PyPI (`curl -s https://pypi.org/pypi/<pkg>/json | jq -r .info.version`) and the installed interpreter — never from trained knowledge.

plugins/devs/skills/python-core/SKILL.md · 46 lines

How it starts

The opening of the file, as written. The whole thing — 46 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Python Core Development

Reference hub for Python work. Verify versions and APIs against PyPI (curl -s https://pypi.org/pypi/<pkg>/json | jq -r .info.version) and the installed interpreter — never from trained knowledge.

Reference routing

Load references on demand — not all at once.

Reference	Use when
type-hints.md	Modern typing: PEP 695 generics, TypeIs, Protocol, strict mypy config
async-patterns.md	TaskGroup, timeouts, queues, blocking-call escape hatches
testing.md	pytest config, fixtures, pytest-asyncio, coverage, async FastAPI tests
fastapi-guide.md	FastAPI services: lifespan, pydantic v2, SQLAlchemy 2 async, auth, CORS
dependencies.md	uv workflow, PEP 735 dependency groups, auditing, moving a project to uv
common-libraries.md	Curated library selection with versions, gotchas, and a do-not-use list

For code-review checklists use the devs:code-review skill; for dependency auditing workflows use devs:deps-core.

Decision guides

Package manager: uv for anything new. In existing projects, detect from the lockfile (poetry.lock → poetry, etc.) and conform — details in dependencies.md.

Data modeling: dataclasses by default; pydantic when runtime validation/serialization is actually needed.

Sync vs async: async only for I/O-bound concurrency (servers, fan-out HTTP); CPU-bound work uses processes or asyncio.to_thread; simple scripts stay sync. Details: async-patterns.md.

Library selection: the curated table (with a do-not-use list) in common-libraries.md.

Performance: profile first (py-spy, scalene); functools.cache for memoization.

Scripts

${CLAUDE_SKILL_DIR}/scripts/init_python_project.sh <name> [package|fastapi] — scaffold via uv init (src layout), append the [tool.*] policy tables, dev tools in the PEP 735 dev group, starter test; self-verifies with ruff + mypy + pytest before reporting success.
${CLAUDE_SKILL_DIR}/scripts/setup_logging.sh — uv add structlog plus a logging_config.py (console on TTY, JSON otherwise); refuses to overwrite an existing one.
${CLAUDE_SKILL_DIR}/scripts/audit_dependencies.sh — uv audit (falling back with instructions when the installed uv predates it) plus uv tree --outdated; non-zero exit on findings or when the vulnerability check cannot run.

Read the full file on GitHub · 46 lines

Files

What ships with it

10 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.

1mo ago First seen · 46 lines · 78 tokens per session scan A d47ceb4e370c

Subscribe to this mod's changes

devs:python-core is a skill published in the GitHub repository aaronbassett/agent-foundry (4 stars, last pushed 2mo ago), licensed MIT. It adds 78 tokens to every session and 826 once invoked, about $0.0003 per session on Opus 5.5. 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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devs:python-core