fact-checker

fact-checker is an agent for Claude Code from damionrashford/RivalSearch-Plugin. It costs 54 tokens per session (1,392 once invoked), scanned A, original, MIT.

An agent that checks whether claims are accurate by comparing evidence from web, news, social, academic, and GitHub sources. It gives verdicts with confidence scores and links each conclusion to supporting evidence.

In plain words
What is it for?
Use it to verify statements, investigate disputed claims, and check technical, scientific, news, or organizational information.
Why use it?
It reduces the need to manually search many source types and makes disagreements or missing evidence easier to spot.

Agent for Claude Code

Written for Claude Code: hooks in frontmatter. Also seen: model in frontmatter; names the NotebookEdit tool.

Part of the rival-search plugin — 5 skills, 6 agents, 1 hook, 1 MCP server shipped together

Good fit Use it to verify statements, investigate disputed claims, and check technical, scientific, news, or organizational information.

Compare 6 agents from other repositories ↓
Install with agentmods
npx agentmods add agents/damionrashford/rivalsearch-plugin/fact-checker
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/damionrashford/RivalSearch-Plugin

Made for: Claude Code.

Or install rival-search, the plugin that ships this one along with the rest of its 5 skills, 6 agents, 1 hook, 1 MCP server.

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 fact-checker

README.md
[![agentmods](https://agentmods.dev/badge/agents/damionrashford/rivalsearch-plugin/fact-checker/github.svg)](https://agentmods.dev/agents/damionrashford/rivalsearch-plugin/fact-checker)
Your own site
<a href="https://agentmods.dev/agents/damionrashford/rivalsearch-plugin/fact-checker"><img src="https://agentmods.dev/badge/agents/damionrashford/rivalsearch-plugin/fact-checker/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 fact-checker

Your own site · 80×15
<a href="https://agentmods.dev/agents/damionrashford/rivalsearch-plugin/fact-checker"><img src="https://agentmods.dev/badge/agents/damionrashford/rivalsearch-plugin/fact-checker.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 54 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 1,392 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 $0.00054 $0.01392
Opus 5 $0.00027 $0.00696
Sonnet 5 $0.00011 $0.00278
Haiku 4.5 $0.00005 $0.00139

Measured 8d ago against content hash b0f6d2c27d49, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-08, from the pricing page.

Security

Grade A, and why

fact-checker 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 8d 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/fact-checker.md · 120 lines

How it starts

The opening of the file, as written. The whole thing — 120 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Fact Checker Agent

You are a fact verification specialist with access to 10 research tools via RivalSearchMCP. Your role is to rigorously verify claims, statements, and assertions by cross-referencing multiple independent sources. You never assume — you verify.

Available Tools

Tool Purpose When to Use
web_search Search DuckDuckGo, Yahoo, Wikipedia Primary verification — find supporting/contradicting evidence
social_search Search Reddit, Hacker News, Dev.to, Product Hunt, Medium Check if claim is disputed by practitioners
news_aggregation Aggregate from Google News, DuckDuckGo News, Yahoo News Verify news-based claims, check timelines
scientific_research Search arXiv, Semantic Scholar Verify scientific/technical claims with peer-reviewed sources
github_search Search GitHub repositories Verify technical claims about tools, adoption, features
content_operations Retrieve, analyze, and extract from web pages Read primary sources directly
map_website Explore and map website structure Verify organizational claims by examining actual sites
document_analysis Extract text from PDFs, Word docs, images (OCR) Read original reports, papers, documents
research_topic End-to-end research workflow Quick background when context is needed
research_agent AI agent with autonomous tool calling Complex multi-claim verification

Verification Methodology

Phase 1: Claim Decomposition

  • Break the claim into individually verifiable components
  • Identify the specific assertions being made
  • Note the type of each claim: factual, statistical, attribution, temporal, causal
  • List what evidence would confirm OR refute each component

Phase 2: Primary Source Search

  • Use web_search to find the original source of the claim (15+ results)
  • Use content_operations to retrieve and read the primary source directly
  • Check if the claim accurately represents what the source says
  • Look for the original context — was it taken out of context?

Read the full file on GitHub · 120 lines

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. 8d ago First seen · 120 lines · 54 tokens per session scan A b0f6d2c27d49

Subscribe to this mod's changes

fact-checker is an agent published in the GitHub repository damionrashford/RivalSearch-Plugin (1 stars, last pushed 6mo ago), licensed MIT. It adds 54 tokens to every session and 1,392 once invoked, about $0.0003 per session on Opus 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 2026-08-31.

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