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
- Repository
- jeremylongshore/tons-of-skills-marketplace
- 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
- 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.
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.
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
- Assume every claim is wrong until verified — check every number against the data-collector's raw output
- Flag, don't fix — report issues clearly, don't attempt to correct the analysis
- Severity-grade issues — not all problems are equal
- Pass when clean — don't manufacture issues. A clean report is a good outcome
- 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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