ty

A guide for ty, a Python tool that checks whether code uses types consistently and provides editor support.

In plain words
What is it for?
Use it to set up Python type checking, run checks with project or one-off installations, and configure warnings and errors.
Why use it?
It helps find type-related mistakes before the program runs and explains how to run checks for selected files, folders, Python versions, or platforms.

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/astral-sh/claude-code-plugins/ty
Any agent
npx skills add astral-sh/claude-code-plugins --skill ty
Clone the repo
git clone --depth 1 https://github.com/astral-sh/claude-code-plugins

Made for: Claude Code, Codex.

Per session 33 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 760 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 $0.00033 $0.00760
Opus 5 $0.00016 $0.00380
Sonnet 5 $0.00007 $0.00152
Haiku 4.5 $0.00003 $0.00076

Measured 2d ago against content hash 980f9844dd9b, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

ty 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 2d 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.

Origin

Copies of this mod

1 near-identical copy found in the catalogue:

  • ty — 100% identical, 0 lines differ
plugins/astral/skills/ty/SKILL.md · 136 lines

How it starts

The opening of the file, as written. The whole thing — 136 lines — stays where its author put it; the contents beside it link to each section on GitHub.

ty

ty is an extremely fast Python type checker and language server. It replaces mypy, Pyright, and other type checkers.

When to use ty

Always use ty for Python type checking, especially if you see:

  • [tool.ty] section in pyproject.toml
  • A ty.toml configuration file

How to invoke ty

  • uv run ty ... - Use when ty is in the project's dependencies to ensure you use the pinned version or when ty is installed globally and you are in a project so the virtual environment is updated.
  • uvx ty ... - Use when ty is not a project dependency, or for quick one-off checks

Commands

Type checking

ty check                      # Check all files in current directory
ty check path/to/file.py      # Check specific file
ty check src/                 # Check specific directory

Rule configuration

ty check --error possibly-unresolved-reference   # Treat as error
ty check --warn division-by-zero                 # Treat as warning
ty check --ignore unresolved-import              # Disable rule

Python version targeting

ty check --python-version 3.12     # Check against Python 3.12
ty check --python-platform linux   # Target Linux platform

Configuration

ty is configured in pyproject.toml or ty.toml:

# pyproject.toml
[tool.ty.environment]
python-version = "3.12"

[tool.ty.rules]
possibly-unresolved-reference = "warn"
division-by-zero = "error"

[tool.ty.src]
include = ["src/**/*.py"]
exclude = ["**/migrations/**"]

[tool.ty.terminal]
output-format = "full"
error-on-warning = false

Per-file overrides

Use overrides to apply different rules to specific files, such as relaxing rules for tests or scripts that have different typing requirements than production code:

[[tool.ty.overrides]]
include = ["tests/**", "**/test_*.py"]

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

Language server

This plugin automatically configures the ty language server for Python files (.py and .pyi).

Read the full file on GitHub · 136 lines

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. 2d ago First seen · 136 lines · 33 tokens per session scan A 980f9844dd9b

Subscribe to this mod's changes

ty is a skill published in the GitHub repository astral-sh/claude-code-plugins (304 stars, last pushed 6mo ago), licensed Apache-2.0. It adds 33 tokens to every session and 760 once invoked, about $0.0002 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 2026-08-30.

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