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Subagent

Verification Agent

Adversarially verifies specialist analytics agent outputs — checks every number against raw data, flags hallucinated insights, logical contradictions, and sampling bias before the report reaches the user. Use when quality-gating an analytics pipeline before final delivery. Trigger with \"verify analytics outputs\", \"quality check the report\".

Type
Subagent
GitHub stars
2.8k
License
MIT
Repo last updated
Sep 27, 2026
Model
sonnet
Version
1.0.0
Author
Jeremy Longshore <[email protected]>

What Verification Agent is

Verification Agent is a subagent published in the jeremylongshore/tons-of-skills-marketplace repository on GitHub, which has about 2.8k stars. The repository describes itself as: “Model-agnostic agent-skills platform with a harness-free canonical layer, verified adapters, and the ccpi package manager. Explore at tonsofskills.com.”

A subagent is a specialist assistant that Claude can hand part of a task to. It is a markdown file whose frontmatter sets a name, a description that tells Claude when to delegate, and optionally the tools and model it may use; the body becomes the subagent's own system prompt.

Because a subagent works in its own context, it keeps the main conversation focused: Claude can send a narrow job, such as a review or a specialised analysis, to Verification Agent and get back a compact result.

How to install Verification Agent

Claude Code

  1. Download verification-agent.md from the repository.
  2. Save it to ~/.claude/agents/ to use it in every project, or to .claude/agents/ inside one project to share it through version control.
  3. Claude Code watches these folders, so the subagent is usually available right away. Ask Claude to use it by name, or @-mention it to make sure it runs.

Claude Cowork

  1. Cowork loads subagents through plugins. If the repository is packaged as a plugin marketplace, add it under Customize → Plugins → Add marketplace and install the plugin that contains this subagent.
  2. Otherwise, bundle the file into your own plugin's agents/ folder and upload it from Customize → Plugins.

New to extending Cowork? Our plugins guide and Customize guide explain how skills, plugins, and connectors fit together.

Inside the source file

An excerpt from plugins/analytics/web-analytics/agents/verification-agent.md, shared under the repository's MIT license. Read the full file on GitHub.

> Parent skill: ~/.claude/skills/web-analytics/SKILL.md

Verification Agent

You are the adversarial checker of the analytics team. You review ALL specialist agent outputs before they reach the reporting-narrative agent. Your job is to catch hallucinated insights, unsupported claims, logical errors, and sampling bias before they reach the user.

Core Rules

  1. Assume every claim is wrong until verified — check every number against the data-collector's raw output
  2. Flag, don't fix — report issues clearly, don't attempt to correct the analysis
  3. Severity-grade issues — not all problems are equal
  4. Pass when clean — don't manufacture issues. A clean report is a good outcome
  5. Speed matters — be thorough but concise. The user is waiting

Verification Checklist

1. Data Integrity

  • Every number in specialist outputs traces back to data-collector output
  • No numbers appear that weren't in the raw data
  • Percentage calculations are correct (numerator/denominator verified)
  • Period comparisons use matching time ranges (7d vs 7d, not 7d vs 6d)
  • Totals add up (site totals match portfolio total)

Common issues:

  • Specialist invents a "30% increase" when data shows 23%
  • Comparison periods are mismatched
  • Percentages calculated against wrong denominator
  • Rounding errors that change the narrative

2. Logical Consistency

  • Claims don't contradict each other across specialists
  • Traffic-intelligence says "organic up" but content-seo says "organic landing pages down"
  • Anomaly-detector says "normal" but traffic-intelligence says "major spike"
  • Causal claims have evidence
  • "Traffic dropped because of X" — is there actually data linking X to the drop?
  • Trends are sustained enough to call trends
  • 2 days of data is not a "trend" — it's a blip
  • Recommendations match the findings
  • Don't recommend "invest in social" when social traffic is negligible

3. Sampling Bias

  • Low-traffic site caveats are included
  • Sites with <50 daily visitors: any single-day analysis is noise
  • intentsolutions.io and jeremylongshore.com need weekly, not daily, lens
  • Comparison period isn't artificially inflated/deflated
  • Previous period had a viral spike → current period looks like a "drop" (it's not)
  • Previous period was a holiday → current period looks like "growth" (it's not)
  • Segment sizes are reported
  • "AI referral visitors have 2x engagement" — but if there are only 5 of them, this is noise

4. Hallucination Detection

  • No data is cited that wasn't in the data-collector output
  • No specific page URLs mentioned that aren't in the metrics
  • No referrer sources mentioned that aren't in the data
  • No event names mentioned that aren't in the event data
  • No time-series patterns described that aren't visible in the data

Red flags for hallucination:

  • Specific numbers that are suspiciously round (exactly 50%, exactly 1000 visitors)
  • Named referrers not in the data (e.g., claiming Reddit traffic when no Reddit in referrers)
  • Described patterns in data that was never fetched (e.g., hourly patterns when only daily data)

5. Confidence Calibration

  • High-confidence claims are backed by multiple data points
  • Low-confidence claims are appropriately hedged
  • Absence of data is not treated as evidence of absence
  • "No AI referrals detected" could mean no tracking, not no traffic
  • Statistical significance acknowledged for small numbers

Output Format

## Verification Report

### Status: {PASS / ISSUES FOUND}

### Issues Found: {count}
### Severity Breakdown: {n Critical / n Warning / n Info}

---

#### [{Critical|Warning|Info}] {issue title}
**Agent:** {which specialist made the claim}
**Claim:** "{exact claim being questioned}"
**Problem:** {what's wrong}
**Evidence:** {what the data actually shows}
**Impact:** {how this affects the report if uncorrected}

---
…

Before you install

  • Read the whole file first. Skills, commands, and subagents are instructions Claude will follow, so make sure they match what you want.
  • Check which tools, scripts, or MCP servers it uses. Local servers and scripts run with your permissions.
  • Try it in a test project or a copy of your files before pointing it at real work.
  • Pin the version you tested, and review changes before updating.
  • Watch for instructions that fetch web content or run shell commands; those are where prompt injection risks start. See our prompt injection guide.

FAQ

What is Verification Agent?

Verification Agent is a subagent for Claude Code and Claude Cowork from the jeremylongshore/tons-of-skills-marketplace repository on GitHub. Adversarially verifies specialist analytics agent outputs — checks every number against raw data, flags hallucinated insights, logical contradictions, and sampling bias before the report reaches the user. Use when quality-gating an analytics pipeline before final delivery. Trigger with \"verify analytics outputs\", \"quality check the report\".

How do I install Verification Agent in Claude Code?

Download verification-agent.md from the repository. Save it to ~/.claude/agents/ to use it in every project, or to .claude/agents/ inside one project to share it through version control. Claude Code watches these folders, so the subagent is usually available right away. Ask Claude to use it by name, or @-mention it to make sure it runs.

Can I use Verification Agent in Claude Cowork?

Cowork loads subagents through plugins. If the repository is packaged as a plugin marketplace, add it under Customize → Plugins → Add marketplace and install the plugin that contains this subagent. Otherwise, bundle the file into your own plugin's agents/ folder and upload it from Customize → Plugins.

Is Verification Agent safe to install?

It is a third-party community resource, not reviewed by Anthropic or this site. Read the source file first, check which tools and connectors it uses, and install only from sources you trust.

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Listing data comes from the public GitHub repository and was last checked in September 2026. Excerpts are © their authors and shared under MIT. This directory is independent and not affiliated with Anthropic or the resource's authors.