designing-zod-schemas

Zod Schema Designer

Overview

Guide the design and implementation of Zod schemas following the project's Zod-first development approach, where schemas are defined before implementing business logic.

When to Use

• Creating new data structures
• Adding validation to inputs
• Designing configuration schemas
• Implementing type-safe transformations
• Creating test data builders

Core Principles

Zod-First Development

1. Define Schema First: Schema is the source of truth
2. Infer Types: Use z.infer<> instead of manual type definitions
3. Share Validation: Same schema for runtime validation and tests
4. Compose Schemas: Build complex schemas from primitives

Decision Guide

Quick Reference

Project Schema Conventions

import { z } from 'zod';

// Slug-based entity (Categories, Products, Channels, etc.)
const SlugSchema = z.string().regex(/^[a-z0-9-]+$/);

// Name-based entity (ProductTypes, Attributes, TaxClasses, etc.)
const NameSchema = z.string().min(1).max(100).trim();

// Branded types for domain safety
const EntitySlugSchema = SlugSchema.transform((v) => v as EntitySlug);

// Standard entity shape
const EntitySchema = z.object({
  name: z.string().min(1),
  slug: z.string().regex(/^[a-z0-9-]+$/),
  description: z.string().optional(),
});

// Always infer types from schemas
type Entity = z.infer<typeof EntitySchema>;

Schema Patterns

For detailed patterns and examples, see:

• Primitive Patterns: Strings, numbers, enums, branded types
• Object Patterns: Objects, discriminated unions, arrays, transforms, refinements
• Testing Patterns: Test data builders, schema validation tests

Project Schema Location

src/modules/config/schema/
├── schema.ts           # Main configuration schema
├── primitives.ts       # Reusable primitive schemas
├── entities/           # Entity-specific schemas
│   ├── category.ts
│   ├── product.ts
│   └── ...
└── index.ts            # Schema exports

Validation Checkpoints

Common Mistakes

External Documentation

For up-to-date Zod patterns, use Context7 MCP:

mcp__context7__get-library-docs with context7CompatibleLibraryID: "/colinhacks/zod"

References

• {baseDir}/src/modules/config/schema/schema.ts - Main schema definitions
• {baseDir}/docs/CODE_QUALITY.md#zod-first-development - Quality standards
• Zod documentation: https://zod.dev

Related Skills

• Complete entity workflow: See adding-entity-types for full schema-to-service implementation
• Testing schemas: See analyzing-test-coverage for test data builders
• GraphQL type mapping: See writing-graphql-operations for schema-to-GraphQL patterns

Quick Reference Rule

For a condensed quick reference, see .claude/rules/config-schema.md (automatically loaded when editing src/modules/config/**/*.ts files).