data-validation-schema-patterns

data-validation-schema-patterns is a skill for Claude Code, Codex from mickeyyaya/refactoring-skills. It costs 90 tokens per session (5,239 once invoked), scanned A, original, MIT.

A code-review guide for checking external data against defined schemas, which describe the allowed shape and values of data.

In plain words
What is it for?
Use it when reviewing APIs, queue messages, uploads, command-line arguments, environment variables, or changes to data contracts.
Why use it?
It helps catch injection risks, corrupted data, crashes, unsafe type coercion, and incompatible schema changes at system boundaries.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit Use it when reviewing APIs, queue messages, uploads, command-line arguments, environment variables…

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Install with agentmods
npx agentmods add skills/mickeyyaya/refactoring-skills/data-validation-schema-patterns
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add mickeyyaya/refactoring-skills --skill data-validation-schema-patterns
Clone the repo
git clone --depth 1 https://github.com/mickeyyaya/refactoring-skills

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for data-validation-schema-patterns

README.md
[![agentmods](https://agentmods.dev/badge/skills/mickeyyaya/refactoring-skills/data-validation-schema-patterns.svg)](https://agentmods.dev/skills/mickeyyaya/refactoring-skills/data-validation-schema-patterns)
Your own site
<a href="https://agentmods.dev/skills/mickeyyaya/refactoring-skills/data-validation-schema-patterns"><img src="https://agentmods.dev/badge/skills/mickeyyaya/refactoring-skills/data-validation-schema-patterns.svg" alt="Measured on agentmods" height="20"></a>
Per session 90 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 5,239 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00090 $0.05239
Opus 5 $0.00045 $0.02619
Sonnet 5 $0.00018 $0.01048
Haiku 4.5 $0.00009 $0.00524

Measured 6d ago against content hash e2bcaea048da, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

data-validation-schema-patterns scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 6d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/data-validation-schema-patterns/SKILL.md · 641 lines

How it starts

The opening of the file, as written. The whole thing — 641 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Data Validation and Schema Patterns for Code Review

Overview

Unvalidated input is the root cause of injection attacks, data corruption, and unexpected crashes. Validation is not a one-time gate at the UI layer — every system boundary must enforce its own schema contract. Use this guide during code review to catch validation hazards before they ship.

When to use: Reviewing code that accepts external data (HTTP requests, queue messages, file uploads, CLI args, environment variables); designing API contracts; evaluating schema evolution for backward compatibility; auditing trust boundaries in internal services.

Quick Reference

Pattern Core Idea Primary Red Flag
Validation Boundary Validate at every trust boundary, not just at the UI Passing raw unknown / any deep into business logic
TypeScript / Zod Runtime schema tied to compile-time type z.any() escapes, skipping .parse() on external data
TypeScript / Joi Rich rule DSL with detailed error messages .unknown(true) without explicit allow-list
TypeScript / io-ts Codec = decoder + encoder, composable Ignoring left branch of Either decode result
Python / Pydantic v2 Model-first validation, high performance model_config = {'arbitrary_types_allowed': True} masking issues
Python / marshmallow Schema-centric, explicit serialization control load() result used without checking validation errors
Python / dataclasses Structural typing only, no runtime enforcement Trusting @dataclass fields have the declared type at runtime
Go / validator Struct tag-based declarative rules Missing binding:"required" tags on mandatory fields
Java / Bean Validation Annotation-driven, integrates with frameworks @Valid missing on nested objects or method parameters
Schema Evolution Additive changes are safe; removals and renames break Removing required fields without a deprecation cycle
Strict vs Coercive Coercion silently accepts wrong types; strict fails fast z.coerce.number() accepting "abc"NaN
Custom Validators Encode business rules as first-class schema constraints Business rule checks scattered outside schema definition

Read the full file on GitHub · 641 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 6d ago First seen · 641 lines · 90 tokens per session scan A e2bcaea048da

Subscribe to this mod's changes

data-validation-schema-patterns is a skill published in the GitHub repository mickeyyaya/refactoring-skills (6 stars, last pushed 5mo ago), licensed MIT. It adds 90 tokens to every session and 5,239 once invoked, about $0.0005 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.