# Export Public Types

> Use when publishing libraries. Use when types appear in public APIs. Use when users need to reference types. Use when building reusable components. Use when designing library interfaces.

- Skill: `marius-townhouse/export-public-types` (Agent Skill)
- Install (CLI): `npx skillmds@latest add marius-townhouse/export-public-types`
- Raw SKILL.md: https://api.skillmd.com/api/skills/marius-townhouse/export-public-types/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: marius-townhouse (https://skillmd.com/u/marius-townhouse)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/marius-townhouse/export-public-types

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# Export All Types That Appear in Public APIs

## Overview

When you publish a library, users need access to all types that appear in your public API. If a function returns `User` but `User` isn't exported, users can't type their own variables to match. Export all types that appear in public function signatures, return types, or interfaces.

This is essential for good developer experience in libraries.

## When to Use This Skill

- Publishing TypeScript libraries
- Types appear in public function signatures
- Users need to reference your types
- Building reusable components
- Designing library interfaces

## The Iron Rule

**Export every type that appears in your public API. Users need these types to work with your library effectively.**

## Example

```typescript
// BAD: Internal type not exported
interface User {
  id: string;
  name: string;
}

export function getUser(id: string): User {
  // ...
}

// User can't do:
// import { getUser, User } from 'library'; // Error: User not exported
// const user: User = getUser('123');

// GOOD: Export the type
export interface User {
  id: string;
  name: string;
}

export function getUser(id: string): User {
  // ...
}

// User can now:
// import { getUser, User } from 'library';
// const user: User = getUser('123');
```

## Reference

- Effective TypeScript, 2nd Edition by Dan Vanderkam
- Item 67: Export All Types That Appear in Public APIs