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Example CLAUDE.md — Minimal

You do not need a long CLAUDE.md to get value from it. This minimal example covers the 80/20 essentials: the commands Claude needs, where things live, and a few key rules. Start here and expand as you discover things Claude gets wrong without guidance.

The CLAUDE.md File

# MyApp

Node.js/Express backend with PostgreSQL.

## Commands

- `npm test` — run tests (Jest)
- `npm test -- --testPathPattern=users` — run tests matching "users"
- `npm run lint` — ESLint check
- `npm run dev` — start dev server

Run `npm run lint && npm test` before committing.

## Structure

- `src/routes/` — API route handlers
- `src/models/` — database models (Sequelize)
- `src/middleware/` — Express middleware
- `tests/` — test files mirroring src/ structure

## Rules

- TypeScript strict mode — no `any`
- All API responses use the format: `{ data, error, status }`
- Use the existing logger (`src/utils/logger.ts`), not console.log

Why This Works

This is only 20 lines, but it tells Claude everything it needs for most tasks:

Commands — Claude knows how to run tests (including a single test), lint, and start the server. The pre-commit instruction ensures Claude runs checks before committing.

Structure — Four lines that prevent Claude from searching the entire codebase. When asked to "add a new endpoint," it knows to look in src/routes/. When asked to "add a model," it goes to src/models/.

Rules — Three rules that would otherwise be violated regularly: - No any prevents the most common TypeScript shortcut - The response format ensures consistency across endpoints - The logger rule prevents scattered console.log statements

When to Add More

Expand your CLAUDE.md when you notice Claude: - Using the wrong coding style repeatedly - Putting files in the wrong directory - Missing a convention that matters to your team - Suggesting libraries or patterns you have decided against

Each time, add one or two lines to address the specific issue. A CLAUDE.md that grows organically from real problems is more useful than one written speculatively.

See Also