json-validator

json-validator is a skill for Claude Code, Codex from koatora20/guard-scanner. It costs 0 tokens per session (163 once invoked), scanned A, original, MIT.

A validator that checks JSON data against JSON Schema rules, such as required fields, data types, and nested properties. JSON Schema is a format for describing the expected structure of JSON.

In plain words
What is it for?
Checking API payloads, configuration files, and other JSON data and returning validation errors.
Why use it?
It identifies data that does not match the structure an application expects before the data is used.

Skill for Claude CodeCodex

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.

agentmods
npx agentmods add skills/koatora20/guard-scanner/json-validator
Any agent
npx skills add koatora20/guard-scanner --skill json-validator
Clone the repo
git clone --depth 1 https://github.com/koatora20/guard-scanner

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 json-validator

README.md
[![agentmods](https://agentmods.dev/badge/skills/koatora20/guard-scanner/json-validator.svg)](https://agentmods.dev/skills/koatora20/guard-scanner/json-validator)
Your own site
<a href="https://agentmods.dev/skills/koatora20/guard-scanner/json-validator"><img src="https://agentmods.dev/badge/skills/koatora20/guard-scanner/json-validator.svg" alt="Measured on agentmods" height="20"></a>
Per session 0 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 163 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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 $0.00000 $0.00163
Opus 5 $0.00000 $0.00081
Sonnet 5 $0.00000 $0.00033
Haiku 4.5 $0.00000 $0.00016

Measured 3d ago against content hash 201cecae1d53, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

json-validator 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 3d 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.

tests/fixtures/benchmark/benign/json-validator/SKILL.md · 28 lines

What it actually says

JSON Schema Validator

Validates JSON data against JSON Schema definitions.

function validate(data, schema) {
  const errors = [];
  if (schema.type && typeof data !== schema.type) {
    errors.push(`Expected ${schema.type}, got ${typeof data}`);
  }
  if (schema.required && Array.isArray(schema.required)) {
    for (const key of schema.required) {
      if (!(key in data)) errors.push(`Missing required: ${key}`);
    }
  }
  if (schema.properties) {
    for (const [key, subSchema] of Object.entries(schema.properties)) {
      if (key in data) {
        errors.push(...validate(data[key], subSchema));
      }
    }
  }
  return errors;
}

module.exports = { validate };
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. 3d ago First seen · 28 lines · 0 tokens per session scan A 201cecae1d53

Subscribe to this mod's changes

json-validator is a skill published in the GitHub repository koatora20/guard-scanner (2 stars, last pushed 2mo ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 163 tokens. 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.