agent-harness: Skill for Claude Code

.agent/SKILLS/mcp-schema-validator/SKILL.md

mcp-schema-validator is a skill for Claude Code, Codex from codejunkie99/agent-harness. It costs 0 tokens per session (104 once invoked), scanned A, original, no licence file.

A validation guide for checking MCP tool schemas and how those tools behave. MCP is a way for AI agents to connect to external tools.

In plain words
What is it for?
Use it when reviewing or testing MCP tools, their input and output schemas, and their expected behavior.
Why use it?
It helps catch incorrect tool definitions and behavior before they cause failures for an agent or its users.

Skill for Claude CodeCodex

Which agent this was written for is unclear — body not stored (licence); the path alone says nothing.

This is codejunkie99/agent-harness's own configuration. It tells Claude Code and Codex how to work on agent-harness itself, so it is not a mod to install elsewhere. Copy it as a starting point and replace the rules that are about this project. Everything agent-harness configures →

Reuse

Borrowing it

Nothing to install: this file belongs to codejunkie99/agent-harness. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file
curl -O https://raw.githubusercontent.com/codejunkie99/agent-harness/main/.agent/SKILLS/mcp-schema-validator/SKILL.md
Clone the repo
git clone --depth 1 https://github.com/codejunkie99/agent-harness

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 mcp-schema-validator

README.md
[![agentmods](https://agentmods.dev/badge/skills/codejunkie99/agent-harness/mcp-schema-validator/github.svg)](https://agentmods.dev/skills/codejunkie99/agent-harness/mcp-schema-validator)
Your own site
<a href="https://agentmods.dev/skills/codejunkie99/agent-harness/mcp-schema-validator"><img src="https://agentmods.dev/badge/skills/codejunkie99/agent-harness/mcp-schema-validator/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for mcp-schema-validator

Your own site · 80×15
<a href="https://agentmods.dev/skills/codejunkie99/agent-harness/mcp-schema-validator"><img src="https://agentmods.dev/badge/skills/codejunkie99/agent-harness/mcp-schema-validator.svg" alt="Reviewed on agentmods" width="80" 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 104 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 unknown 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 $0.00000 $0.00104
Opus 5.5 $0.00000 $0.00042
Sonnet 5.5 $0.00000 $0.00021
Haiku 4.5 $0.00000 $0.00010

Measured 2mo ago against content hash 2ecc05e3a23a, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

mcp-schema-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 2mo 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.

.agent/SKILLS/mcp-schema-validator/SKILL.md · 16 lines

The source is not reproduced here

No licence file

A repository with no LICENSE is all rights reserved by default, so the body is not copied here. The metadata, the measurements and the link are.

Read it on GitHub

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. 2mo ago First seen · 16 lines · 0 tokens per session scan A 2ecc05e3a23a

Subscribe to this mod's changes

mcp-schema-validator is a skill published in the GitHub repository codejunkie99/agent-harness (14 stars, last pushed 5mo ago), with no licence file. It costs nothing until one of its globs matches a file; then it loads 104 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.

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