ty-skills

ty-skills is a skill for Claude Code, Codex from jiatastic/open-python-skills. It costs 104 tokens per session (944 once invoked), scanned A, original, MIT.

A set of instructions for using ty, a Python type checker that finds places where values or function arguments may have the wrong type. It covers setup, rules, configuration, and migration from other type checkers.

In plain words
What is it for?
Use it to add or fix Python type annotations, run checks on files or folders, configure diagnostics in pyproject.toml, and move from mypy or pyright.
Why use it?
It finds many type-related mistakes before the program runs and makes those checks repeatable in editors and continuous integration.

Skill for Claude CodeCodex

Part of the open-python-skills plugin — 8 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/jiatastic/open-python-skills/ty-skills
Any agent
npx skills add jiatastic/open-python-skills --skill ty-skills
Clone the repo
git clone --depth 1 https://github.com/jiatastic/open-python-skills

Made for: Claude Code, Codex.

Or install open-python-skills, the plugin that ships this one along with the rest of its 8 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 ty-skills

README.md
[![agentmods](https://agentmods.dev/badge/skills/jiatastic/open-python-skills/ty-skills.svg)](https://agentmods.dev/skills/jiatastic/open-python-skills/ty-skills)
Your own site
<a href="https://agentmods.dev/skills/jiatastic/open-python-skills/ty-skills"><img src="https://agentmods.dev/badge/skills/jiatastic/open-python-skills/ty-skills.svg" alt="Measured on agentmods" height="20"></a>
Per session 104 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 944 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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 $0.00104 $0.00944
Opus 5 $0.00052 $0.00472
Sonnet 5 $0.00021 $0.00189
Haiku 4.5 $0.00010 $0.00094

Measured 5d ago against content hash 865d747c55cd, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

ty-skills 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 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.

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.

skills/ty-skills/SKILL.md · 131 lines

How it starts

The opening of the file, as written. The whole thing — 131 lines — stays where its author put it; the contents beside it link to each section on GitHub.

ty-skills

Master Python type checking with ty - the extremely fast type checker written in Rust by Astral (creators of uv and Ruff).

When to Use This Skill

  • Adding type annotations to Python code
  • Fixing type errors and diagnostics from ty
  • Configuring ty rules and severity levels
  • Migrating from mypy or pyright to ty
  • Understanding advanced type patterns (intersection types, protocols, generics)
  • Setting up ty language server in your editor

Quick Start

# Install
uv tool install ty
# or: pip install ty

# Check current directory
ty check

# Check specific files
ty check src/

# Full diagnostics
ty check --output-format full

Configuration

Configure via pyproject.toml:

[tool.ty.environment]
python-version = "3.12"
python = "./.venv"
python-platform = "linux"
root = ["./src"]
extra-paths = ["./typings"]

[tool.ty.rules]
# error: fail CI, warn: report, ignore: disable
possibly-unresolved-reference = "error"
invalid-argument-type = "error"
division-by-zero = "warn"
unused-ignore-comment = "warn"

[tool.ty.src]
include = ["src", "tests"]
exclude = ["src/migrations/"]

# Per-file overrides
[[tool.ty.overrides]]
include = ["tests/**"]

[tool.ty.overrides.rules]
possibly-unresolved-reference = "warn"

Rules Quick Reference

Rule Default Description
possibly-unresolved-reference error Variable might not be defined
invalid-argument-type error Argument type mismatch
incompatible-assignment error Assigned value incompatible
missing-argument error Required argument missing
unsupported-operator error Operator not supported for types
invalid-return-type error Return type mismatch
division-by-zero warn Potential division by zero
unused-ignore-comment warn Suppression not needed
redundant-cast warn Cast has no effect
possibly-unbound-attribute warn Attribute might not exist
index-out-of-bounds warn Index might be out of range

Read the full file on GitHub · 131 lines

Files

What ships with it

8 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. 5d ago First seen · 131 lines · 104 tokens per session scan A 865d747c55cd

Subscribe to this mod's changes

ty-skills is a skill published in the GitHub repository jiatastic/open-python-skills (9 stars, last pushed 7mo ago), licensed MIT. It adds 104 tokens to every session and 944 once invoked, about $0.0005 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 2026-08-31.

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