Zod Skill

Created by Anivar Aravind

An AI agent skill for writing, validating, and debugging Zod v4 schemas with modern best practices.

The Problem

AI agents often generate outdated Zod v3 patterns — z.string().email() instead of z.email(), z.nativeEnum() instead of the unified z.enum(), required_error instead of the error parameter — and miss critical parsing pitfalls like using parse() instead of safeParse(), forgetting parseAsync for async refinements, or assuming z.object() preserves unknown keys. These produce schemas that compile but silently misbehave at runtime.

This Solution

27 rules with incorrect→correct code examples that teach agents Zod v4's actual API behavior, schema design patterns, error handling, architectural placement, observability, and TypeScript integration. Each rule targets a specific mistake and shows exactly how to fix it.

Install

npx skills add anivar/zod-skill -g

Testing schemas is covered too, merged from the former zod-testing skill — see references/testing.md.

Or with full URL:

npx skills add https://github.com/anivar/zod-skill

Baseline

• zod ^4.3.0 (tracks 4.4.x; audited against zod.dev, August 2026)
• TypeScript ^5.5

The skill is checked against Zod's own documentation rather than its release notes, which matters more than it sounds: several APIs announced in 4.3 releases — slugify, .with(), .apply(), .overwrite(), .register() — have no presence in the documentation, and a skill that taught them would be teaching an interface the project has not committed to.

What's Inside

27 Rules Across 9 Categories

Priority	Category	Rules	Impact
1	Parsing & Type Safety	3	CRITICAL
2	Schema Design	4	CRITICAL
3	Refinements & Transforms	3	HIGH
4	Error Handling	3	HIGH
5	Performance & Composition	3	MEDIUM
6	v4 Migration	3	MEDIUM
7	Advanced Patterns	3	MEDIUM
8	Architecture & Boundaries	3	CRITICAL/HIGH
9	Observability	2	HIGH/MEDIUM

Each rule file contains:

• Why it matters
• Incorrect code with explanation
• Correct code with explanation
• Decision tables and additional context

9 Deep-Dive References

Reference	Covers
schema-types.md	All primitives, string formats, numbers, enums, dates, files, JSON
parsing-and-inference.md	parse, safeParse, parseAsync, z.infer, z.input, coercion
objects-and-composition.md	object/strict/loose, pick, omit, partial, recursive, unions, tuples
refinements-and-transforms.md	refine, superRefine, transform, pipe, defaults, catch
error-handling.md	ZodError, flattenError, treeifyError, error customization, i18n
advanced-features.md	Codecs, branded types, JSON Schema, registries, Standard Schema
anti-patterns.md	14 common mistakes with BAD/GOOD examples
boundary-architecture.md	Where Zod fits: Express, tRPC, Next.js, React Hook Form, env, external APIs
linter-and-ci.md	ESLint rules, CI schema snapshots, unused schema detection, circular deps

Structure

├── SKILL.md                          # Entry point for AI agents
├── AGENTS.md                         # Compiled guide with all rules expanded
├── rules/                            # Individual rules (Incorrect→Correct)
│   ├── parse-*                       # Parsing & type safety (CRITICAL)
│   ├── schema-*                      # Schema design (CRITICAL)
│   ├── refine-*                      # Refinements & transforms (HIGH)
│   ├── error-*                       # Error handling (HIGH)
│   ├── perf-*                        # Performance & composition (MEDIUM)
│   ├── migrate-*                     # v4 migration (MEDIUM)
│   ├── pattern-*                     # Advanced patterns (MEDIUM)
│   ├── arch-*                        # Architecture & boundaries (CRITICAL/HIGH)
│   └── observe-*                     # Observability (HIGH/MEDIUM)
└── references/                       # Deep-dive reference docs
    ├── schema-types.md
    ├── parsing-and-inference.md
    ├── objects-and-composition.md
    ├── refinements-and-transforms.md
    ├── error-handling.md
    ├── advanced-features.md
    ├── anti-patterns.md
    ├── boundary-architecture.md
    └── linter-and-ci.md

Ecosystem — Skills by Anivar Aravind

Testing Skills

Skill	What it covers	Install
jest-skill	Jest best practices — mock design, async testing, matchers, timers, snapshots	npx skills add anivar/jest-skill -g
zod-testing	Zod schema testing — safeParse, mock data, property-based	npx skills add anivar/zod-testing -g
msw-skill	MSW 2.0 API mocking — handlers, responses, GraphQL	npx skills add anivar/msw-skill -g
redux-saga-testing	Redux-Saga testing — expectSaga, testSaga, providers	npx skills add anivar/redux-saga-testing -g

Library & Framework Skills

Skill	What it covers	Install
redux-saga-skill	Redux-Saga effects, fork model, channels, RTK	npx skills add anivar/redux-saga-skill -g
msw-skill	MSW 2.0 handlers, responses, migration	npx skills add anivar/msw-skill -g

Engineering Analysis

Skill	What it covers	Install
contributor-codebase-analyzer	Code analysis, annual reviews, promotion readiness	npx skills add anivar/contributor-codebase-analyzer -g

Author

Anivar Aravind — Building AI agent skills for modern JavaScript/TypeScript development.

License

MIT

If this is useful

A star helps other people find it, and tells me which of these skills are worth keeping current as the upstream libraries move.

Sponsor the work if you would like more of it — these skills are maintained alongside open standards and small-model work at OpenSLM.