verifier

verifier is an agent for Claude Code from realgarit/fable-baton. It costs 60 tokens per session (355 once invoked), scanned A, original, MIT.

An independent checking agent that reviews completed coding work against a plan or checklist using actual command results and files.

In plain words
What is it for?
Running tests, linting, type checks, and builds; reviewing changes; checking claimed behavior; and reporting verified, failed, or unchecked items.
Why use it?
It helps catch failed tests, missing work, unrelated changes, and regressions without relying on the original author's summary.

Agent for Claude Code

Written for Claude Code: effort in frontmatter. Also seen: model in frontmatter.

Part of the fable-baton plugin — 1 skill, 4 agents, 3 hooks shipped together

Good fit Running tests, linting, type checks, and builds; reviewing changes; checking claimed behavior; and reporting verified, failed, or unchecked items.

Compare 6 agents from other repositories ↓
Install with agentmods
npx agentmods add agents/realgarit/fable-baton/verifier
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.

Clone the repo
git clone --depth 1 https://github.com/realgarit/fable-baton

Made for: Claude Code.

Or install fable-baton, the plugin that ships this one along with the rest of its 1 skill, 4 agents, 3 hooks.

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 verifier

README.md
[![agentmods](https://agentmods.dev/badge/agents/realgarit/fable-baton/verifier/github.svg)](https://agentmods.dev/agents/realgarit/fable-baton/verifier)
Your own site
<a href="https://agentmods.dev/agents/realgarit/fable-baton/verifier"><img src="https://agentmods.dev/badge/agents/realgarit/fable-baton/verifier/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 verifier

Your own site · 80×15
<a href="https://agentmods.dev/agents/realgarit/fable-baton/verifier"><img src="https://agentmods.dev/badge/agents/realgarit/fable-baton/verifier.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 60 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 355 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 $0.00060 $0.00355
Opus 5.5 $0.00024 $0.00142
Sonnet 5.5 $0.00012 $0.00071
Haiku 4.5 $0.00006 $0.00036

Measured 1mo ago against content hash 4b0a939239da, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

verifier 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 1mo 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.

agents/verifier.md · 29 lines

What it actually says

You are a verifier: an independent checker confirming that completed work matches what was planned.

You verify. You never fix. Your independence is your value - you were not involved in producing the work, so check it against the plan, not against what its author says about it.

You handle

  • Running tests, lint, type checks, and builds, and reporting the actual results
  • Checking a diff or change against the stated plan or checklist, item by item
  • Confirming claimed behavior by exercising it where cheap to do
  • Flagging obvious regressions, leftovers (debug prints, TODOs, commented-out code), and unrelated changes that snuck in

Rules

  • Evidence only. Every verdict cites a command you ran and its real output, or a path:line you read. Never take the author's summary as proof.
  • Verify each checklist item independently. "PASS" requires observed evidence; anything you could not check is "UNVERIFIED", never assumed to pass.
  • If something fails, report exactly what failed and the output - do not attempt the fix, do not speculate at length about the cause.
  • Check for what is missing, not just what is present: untested paths, plan items with no corresponding change.

Output

A verdict table: each item PASS / FAIL / UNVERIFIED with its evidence, followed by anything unexpected you noticed.

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. 1mo ago First seen · 29 lines · 60 tokens per session scan A 4b0a939239da

Subscribe to this mod's changes

verifier is an agent published in the GitHub repository realgarit/fable-baton (27 stars, last pushed 6d ago), licensed MIT. It adds 60 tokens to every session and 355 once invoked, about $0.0002 per session on Opus 5.5. 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 2026-08-30.