Guide · Agent skill
How to use the Python Type Safety agent skill
Updated · written with AI from the project's own documentation and checked against our catalogue data
The Python Type Safety skill is a set of Python typing guidelines that an AI agent follows when you ask it to add type annotations, write generic classes, define protocol interfaces, or configure mypy or pyright. It is written for Python developers who want the agent to produce typed code. After this guide you will know how to install the skill, how to phrase requests so it triggers, and what to check before relying on its output.
Python Type Safetywshobson/agents · MIT Download the skill Quick start
- 1Download the ZIP. Download the python-type-safety skill ZIP from this page.
- 2Unzip into a skills folder. Unzip it into ~/.claude/skills/ for personal use, or into your project's .claude/skills/ folder.
- 3Or upload in the Claude apps. In the Claude apps, go to Settings → Capabilities → Skills and upload the skill.
- 4Install mypy or pyright. Install a type checker yourself, since the skill does not bundle one.
- 5Ask for typing work. Make a request such as adding type hints or defining a Protocol. The skill loads when the request matches its description.
- 6Run the checker. Run mypy --strict or pyright on the changed code and review the agent's annotations.
What the skill makes the agent do
The skill is a guidance document, not a tool. It does not run type checkers itself. Instead it changes how the agent writes Python when typing work is requested. It describes four core ideas: type annotations for parameters, return values and variables; generics that keep type information across different types; protocols that define structural interfaces without inheritance; and type narrowing with guards and conditionals.
- Annotate all public functions, methods and classes
- Prefer modern union syntax such as X | None on Python 3.10+
- Narrow types with guards so the checker knows what a value is
- Suggest running mypy --strict or pyright in CI
- Minimise Any, using specific types or generics instead
- Bound type variables and create named type aliases for complex types
Install the Python Type Safety skill
Download the skill ZIP from this page and unzip it. You can install it in one of two places. For a personal setup that applies across projects, unzip it into ~/.claude/skills/. For a single project, unzip it into the project's .claude/skills/ folder. The skill folder contains SKILL.md and references/details.md.
If you use the Claude apps, you can instead upload the skill under Settings → Capabilities → Skills.
- Personal: ~/.claude/skills/
- Project only: .claude/skills/ inside your project
- Claude apps: Settings → Capabilities → Skills, then upload
Trigger the skill with natural requests
The skill loads when your request matches its description. You do not need a special command. Ask for typing work in plain language, naming the task that matches the skill's scope.
- Add type hints to this module so mypy --strict passes
- Make this repository class generic over the entity and ID types
- Define a Protocol for the storage backends this service accepts
- Set up pyright for this project and explain the config
- Narrow the Optional user returned by find_user before using it
Examples of what the output looks like
Given a function that may find nothing, the skill steers the agent toward an explicit return type and a guard. The skill's own example uses a signature returning User | None, then raises an error when the value is None so the type checker knows the rest of the block has a User.
For generic containers, the skill includes a Result class parameterised by a value type T and a bounded error type E, with unwrap and unwrap_or methods. For data access, its reference file shows a generic abstract Repository over an entity type T and an identifier type ID, with a concrete UserRepository subclass using string IDs.
def get_user(user_id: str) -> User | None:
"""Return type makes 'might not exist' explicit."""
...
user = get_user("123")
if user is None:
raise UserNotFoundError("123")
print(user.name) # Type checker knows user is User hereWhat you need before using it
The skill recommends Python 3.10 or newer for the modern union syntax it shows. For older code, it notes that Optional[T] and Union still work and are needed for Python 3.9. The skill does not bundle a type checker, so you need mypy or pyright installed for the checking workflows it describes.
- Python 3.10+ recommended (Optional and Union for 3.9)
- mypy or pyright, installed separately
- Runs scripts: no
- Uses network: no
Safety notes on scripts and network
According to the skill's listing, it does not run scripts and does not use the network. It is made of Markdown guidance files. Its effect comes from changing the code the agent writes, so you should still review generated annotations and run your own type checker, because the agent's code is only as correct as the checks you run.
- Scripts: none run
- Network: none used
- Review generated code and run mypy or pyright yourself
Tips for getting good results
For existing projects, the skill suggests enabling strict mode incrementally with per-module overrides rather than all at once. Ask the agent to annotate public signatures first, then tighten internal modules. Keep Any for truly dynamic data or code that calls untyped third-party libraries.
- Start with public APIs, then internal modules
- Use per-module overrides to adopt strict mode gradually
- Ask for type aliases when a type expression gets long
- Accept Any only for dynamic data or untyped third-party code
What people use it for
- Adding type hints to an existing Python codebase, starting with public functions and classes
- Writing a typed public API for a library so users get accurate editor and checker feedback
- Defining a Protocol for a service that accepts several interchangeable backends
- Making a repository or container class generic so its return types match the stored type
- Setting up mypy --strict or pyright configuration for a team's CI
Frequently asked questions
How do I install the Python Type Safety agent skill?
Download the skill ZIP from this page and unzip it into ~/.claude/skills/ for personal use, or into a project's .claude/skills/ folder. In the Claude apps you can instead upload it under Settings → Capabilities → Skills.
What does the python-type-safety skill require?
It recommends Python 3.10 or newer for the modern union syntax, and mypy or pyright for the type checking workflows. Those type checkers are not bundled, so install them separately. The skill runs no scripts and uses no network.
Is the Python Type Safety skill free?
The skill is listed under the MIT licence. This page does not state pricing beyond that licence, so check the source repository for the licence terms.
Does the skill run mypy or pyright for me?
No. It is a guidance document that changes how the agent writes Python code. You still need to run mypy --strict or pyright yourself, for example in CI.
Why does the agent suggest X | None instead of Optional[X]?
The skill prefers the modern union syntax on Python 3.10+. It notes that Optional and Union are still valid and are needed for Python 3.9.
Can I use this skill for a non-Python project or a quick script?
It is not suited to non-Python projects because its guidance is specific to Python typing. For quick scripts, full annotations may add effort without much benefit, since strict typing matters most for maintained code.
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Our verdict
Use this skill if you work on maintained Python code, want typed public APIs, or are setting up mypy or pyright for a team. Pick something else for non-Python projects or throwaway scripts, where its strict annotation guidance adds effort without much value. Because it only shapes what the agent writes, you will still need to run a type checker to confirm the results.
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