python-fastapi-ddd-skill

A collection of Agent Skills for designing FastAPI backends in Python using Domain-Driven Design (DDD) and Onion Architecture patterns.

This skill is based on the reference implementation:

• dddpy: https://github.com/iktakahiro/dddpy

Skills

Skill	Description
python-fastapi-ddd-skill	Architecture + core DDD patterns (Entities, Value Objects, Repositories, UseCases)
python-fastapi-ddd-presentation-skill	FastAPI handlers, Pydantic schemas, error mapping
python-fastapi-ddd-testing-skill	pytest patterns for Domain / UseCase layers
python-fastapi-ddd-tooling-skill	uv / ruff / mypy / pytest / CI templates

Install

Claude Code (recommended)

Register this repository as a plugin marketplace, then install:

# 1. Register the marketplace
/plugin marketplace add iktakahiro/python-fastapi-ddd-skill

# 2. Install all skills at once
/plugin install python-fastapi-ddd@python-fastapi-ddd-skills

Or browse and install interactively:

/plugin
# → "Browse and install plugins"
# → "python-fastapi-ddd-skills"
# → "python-fastapi-ddd"
# → "Install now"

OpenAI Codex

Via skill installer

python3 ~/.codex/skills/.system/skill-installer/scripts/install-skill-from-github.py \
  --repo iktakahiro/python-fastapi-ddd-skill \
  --path skills/python-fastapi-ddd-skill

Install the other skills by changing --path to one of:

• skills/python-fastapi-ddd-presentation-skill
• skills/python-fastapi-ddd-testing-skill
• skills/python-fastapi-ddd-tooling-skill

Then restart Codex to pick up the new skill.

Manual install (copy the folder)

dest="${CODEX_HOME:-$HOME/.codex}/skills"
mkdir -p "$dest"
cp -R skills/python-fastapi-ddd-skill "$dest/"

You can also copy any of:

• skills/python-fastapi-ddd-presentation-skill
• skills/python-fastapi-ddd-testing-skill
• skills/python-fastapi-ddd-tooling-skill

Then restart Codex to pick up the new skill.

Usage

Once installed, mention the skill in your prompt:

Design a FastAPI + SQLAlchemy service with DDD and Onion Architecture.

Implement FastAPI handlers/schemas that call UseCases and map Domain errors to HTTP responses.

Add pytest unit tests for Value Objects and UseCases (mocking repository interfaces).

Set up uv + Makefile + ruff/mypy/pytest + GitHub Actions CI for this project.

License

Apache-2.0