Agent Skills: Project Structure Skill

Project Structure Skill

Use this skill when organizing a new project, refactoring structure, or evaluating project layout.

General Principles

• Discoverability: New developers should find things where they expect them.
• Cohesion: Related code lives together.
• Separation of concerns: Different responsibilities in different modules.
• Flat over nested: Avoid deep directory hierarchies when possible.
• Consistency: Follow the same patterns throughout the project.

Common Directory Patterns

Source Code

src/           # Application source code
lib/           # Library/utility code
pkg/           # Go packages (Go convention)
internal/      # Private packages (Go convention)

Tests

tests/         # Test files (separate from source)
__tests__/     # Jest/Vitest convention
*_test.go      # Go convention (alongside source)
*_test.py      # pytest can discover anywhere
test_*.py      # pytest prefix convention

Configuration

config/        # Configuration files
.env           # Environment variables (git-ignored)
.env.example   # Example environment template (committed)

Documentation

docs/          # Documentation
README.md      # Project overview
CONTRIBUTING.md # Contribution guidelines
CHANGELOG.md   # Version history

Build/Output

build/         # Build output (git-ignored)
dist/          # Distribution files (git-ignored)
out/           # Output directory (git-ignored)
bin/           # Compiled binaries (git-ignored)

Language-Specific Layouts

Python

project/
├── src/
│   └── package_name/
│       ├── __init__.py
│       ├── main.py
│       ├── models/
│       ├── services/
│       └── api/
├── tests/
│   ├── conftest.py
│   ├── test_main.py
│   └── ...
├── pyproject.toml
├── requirements.txt (or requirements-dev.txt)
└── README.md

TypeScript/React

project/
├── src/
│   ├── components/
│   │   ├── Button/
│   │   │   ├── Button.tsx
│   │   │   ├── Button.test.tsx
│   │   │   └── index.ts
│   │   └── ...
│   ├── hooks/
│   ├── services/
│   ├── types/
│   ├── utils/
│   └── App.tsx
├── public/
├── tests/
├── package.json
├── tsconfig.json
└── README.md

Go

project/
├── cmd/
│   └── appname/
│       └── main.go
├── internal/
│   ├── handler/
│   ├── service/
│   ├── repository/
│   └── model/
├── pkg/            # Public packages (if library)
├── api/            # API definitions (OpenAPI, protobuf)
├── go.mod
├── go.sum
└── README.md

Module Organization

By Feature (Recommended for Applications)

src/
├── users/
│   ├── handler.py
│   ├── service.py
│   ├── repository.py
│   └── models.py
├── orders/
│   ├── handler.py
│   ├── service.py
│   ├── repository.py
│   └── models.py
└── ...

By Layer (Common but Less Scalable)

src/
├── handlers/
│   ├── users.py
│   └── orders.py
├── services/
│   ├── users.py
│   └── orders.py
├── repositories/
│   ├── users.py
│   └── orders.py
└── models/
    ├── user.py
    └── order.py

Feature-based organization scales better as the codebase grows.

File Naming Conventions

General

• Use lowercase with separators: user_service.py, user-service.ts
• Be descriptive: email_validator.py not validator.py
• Match the primary export: UserService class in user_service.py

Language-Specific

• Python: snake_case.py
• TypeScript: kebab-case.ts or PascalCase.tsx for components
• Go: lowercase.go (no separators)

Test Files

• Python: test_*.py or *_test.py
• TypeScript: *.test.ts, *.spec.ts
• Go: *_test.go

Configuration Management

Environment Variables

• Use .env for local development (git-ignored)
• Provide .env.example with dummy values (committed)
• Load with appropriate library (python-dotenv, dotenv)
• Validate required variables at startup

Configuration Files

• Keep configuration separate from code
• Use typed configuration objects
• Validate configuration on load
• Support environment-specific overrides

Dependency Management

Lockfiles

Always commit lockfiles for reproducible builds:

• package-lock.json / yarn.lock / bun.lockb
• poetry.lock / requirements.txt (pinned)
• go.sum

Virtual Environments

• Python: Use venv or poetry
• Node: Use node_modules (project-local by default)
• Go: Uses module cache (system-wide)

Git Organization

.gitignore Essentials

# Dependencies
node_modules/
venv/
.venv/

# Build output
build/
dist/
*.pyc
__pycache__/

# Environment
.env
.env.local

# IDE
.idea/
.vscode/
*.swp

# OS
.DS_Store
Thumbs.db

Essential Root Files

README.md          # What is this project?
LICENSE            # How can others use it?
CONTRIBUTING.md    # How to contribute?
CHANGELOG.md       # What changed?
.gitignore         # What to exclude?
.editorconfig      # Editor settings