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¶

```markdown

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.