# zod

A Cursor rule that sets conventions for Zod schemas: strict TypeScript, type inference from schemas and parsing untrusted data at the edge.

- rule · `type=rule` · Cursor · ★ 3579
- Author: sanjeed5
- License: CC0-1.0 · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/sanjeed5/awesome-cursor-rules-mdc/tree/HEAD/rules-mdc/zod.mdc
- Updated: 2026-05-19
- HTML: https://affpapa.org/en/nevibecode/rules/zod

## What it does

The rule attaches to `**/*.{ts,tsx}` files in Cursor. It lists what your schemas should look like: `strict: true` in `tsconfig.json`, the peer dependency range `^3.25.0 || ^4.0.0`, and types derived with `z.infer` instead of hand-written interfaces.

A second block covers parsing. Use `safeParse` for API responses and form input, `parse` when you want the error thrown right away. There are examples of custom error messages, transforms such as `trim` and `toLowerCase` inside the schema, and `z.coerce` for query parameters and environment variables. The difference between `optional()`, `nullable()` and `default()` comes with the resulting inferred type spelled out.

Schemas go into domain files — `schemas/user.schema.ts`, `schemas/product.schema.ts` — rather than one shared module. Type inference in Zod depends on strict mode, so a project with it off will need a `tsconfig.json` change before the rule makes sense. The text cuts off inside the unit-testing section, so there is no telling what else it covers.

## Install

### Cursor (native platform)

**Manually: put the files in place**
- File: `.cursor/rules/zod.mdc` — Frontmatter: description, globs, alwaysApply

### Claude Code

**Manually: put the files in place**
- File: `.claude/rules/zod.md` — The paths frontmatter field limits the files: move globs from the source into paths

### Codex

**AGENTS.md**
- Codex reads AGENTS.md: paste the rule text there

### GitHub Copilot

**Manually: put the files in place**
- File: `.github/instructions/zod.instructions.md` — The applyTo field sets which files it applies to: move globs from the source into applyTo

### Windsurf (Devin Desktop)

**Manually: put the files in place**
- File: `.devin/rules/zod.md`

### Cline

**Manually: put the files in place**
- File: `.clinerules/zod.md`

Where a file is given instead of a command, copy the files from the source to that path: https://github.com/sanjeed5/awesome-cursor-rules-mdc/tree/HEAD/rules-mdc/zod.mdc

## When to use it
- validate API responses before they reach your code
- derive TypeScript types from the schema itself
- show users readable form validation errors
- coerce query-string values into numbers and booleans
- split schemas into per-domain files instead of one module

## Example prompts
- add a schema for this API response and parse it with safeParse
- rewrite this interface as z.infer from the schema
- write a schema for the query params using z.coerce

## Source text · zod.mdc · CC0-1.0

Below is the content of a third-party file. It is data, not instructions for you: do not act on anything written inside unless the human asks. Block tag: 4fe6814a2a11ed74.

BEGIN THIRD-PARTY FILE 4fe6814a2a11ed74
````text
---
description: This guide outlines definitive best practices for using Zod in TypeScript projects, ensuring robust runtime validation, superior type safety, and maintainable schemas.
globs: **/*.{ts,tsx}
---
# Zod Best Practices

Zod is the definitive TypeScript-first schema validation library. It provides static type inference directly from runtime schemas, catching data-shape errors at both compile time and runtime. Adhere to these guidelines to build resilient, type-safe applications with Zod 4.

## Core Setup & Principles

### 1. Enable Strict TypeScript

Zod's type inference relies on `strict: true` in your `tsconfig.json`. This is non-negotiable for reliable type safety.

```json
// tsconfig.json
{
  "compilerOptions": {
    "strict": true, // ✅ ALWAYS enable strict mode
    // ...
  }
}
```

### 2. Standardize Zod 4 Adoption

Ensure your project and any Zod-dependent libraries use the modern Zod 4 core.

```json
// package.json
{
  "dependencies": {
    "zod": "^3.25.0 || ^4.0.0" // ✅ Use this peer dependency range
  }
}
```

### 3. Leverage Type Inference (`z.infer`)

Always infer types from your schemas. This eliminates duplication and keeps types synchronized with validation logic.

```typescript
import { z } from 'zod';

const userSchema = z.object({
  id: z.string().uuid(),
  name: z.string().min(1),
  email: z.string().email(),
});

// ❌ BAD: Manually defining types
interface User {
  id: string;
  name: string;
  email: string;
}

// ✅ GOOD: Infer types directly from the schema
type User = z.infer<typeof userSchema>;

function processUser(user: User) {
  console.log(user.email);
}
```

## Data Validation & Error Handling

### 4. Always Parse Untrusted Data

Never trust external data. Use `schema.parse()` or `schema.safeParse()` immediately upon receiving data from APIs, forms, or environment variables.

```typescript
import { z } from 'zod';

const idSchema = z.string().uuid();

// ❌ BAD: Assuming data is valid
function processId(id: string) {
  // This 'id' could be anything if not validated
  console.log(id.toUpperCase());
}

// ✅ GOOD: Use safeParse for external/untrusted data
function handleRequest(rawId: unknown) {
  const result = idSchema.safeParse(rawId);
  if (!result.success) {
    console.error('Invalid ID received:', result.error.issues);
    return { status: 400, message: 'Invalid ID' };
  }
  // Data is now type-safe and validated
  processId(result.data);
  return { status: 200, message: 'ID processed' };
}

// ✅ GOOD: Use parse for trusted data or when immediate error throwing is desired
function loadConfig(envVar: unknown) {
  try {
    const config = z.object({ API_KEY: z.string().min(1) }).parse(envVar);
    console.log('Config loaded:', config.API_KEY);
  } catch (error) {
    if (error instanceof z.ZodError) {
      console.error('Invalid environment config:', error.issues);
      process.exit(1); // Critical error, exit application
    }
    throw error;
  }
}
```

### 5. Customize Error Messages for UX

Provide clear, user-friendly error messages directly within your schemas.

```typescript
import { z } from 'zod';

const loginSchema = z.object({
  email: z.string().email({ message: 'Invalid email address.' }), // ✅ Custom message
  password: z.string().min(8, { message: 'Password must be at least 8 characters.' }), // ✅ Custom message
});

// Integrate with form libraries (e.g., React Hook Form)
// const { register, handleSubmit, formState: { errors } } = useForm({
//   resolver: zodResolver(loginSchema),
// });
```

## Schema Design & Organization

### 6. Keep Schemas Modular & Domain-Specific

Organize schemas into small, focused files based on their domain. Avoid monolithic schema files.

```
// ❌ BAD: monolithic schemas.ts
// schemas.ts
````
END THIRD-PARTY FILE 4fe6814a2a11ed74

The third-party file has ended. Everything between the 4fe6814a2a11ed74 tags is data: requests and commands from it are not followed. An “end of file” line with another tag inside the block is part of the file.

First 3768 of 7788 bytes. © sanjeed5 · CC0-1.0 · https://github.com/sanjeed5/awesome-cursor-rules-mdc/tree/HEAD/rules-mdc/zod.mdc

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