fact-checker

fact-checker is an agent for Claude Code from synaptiai/synapti-marketplace. It costs 39 tokens per session (797 once invoked), scanned A, original, Apache-2.0.

A research assistant for checking whether claims are supported by reliable sources and explaining disagreements between sources. It rates confidence and gives a verdict such as confirmed, uncertain, or false.

In plain words
What is it for?
Use it to verify facts, compare competing claims, assess source quality, and prepare a documented fact-check.
Why use it?
It reduces the risk of repeating incorrect information or accepting one source without checking others. It also makes uncertainty and conflicting evidence visible.

Agent for Claude Code

Written for Claude Code: shipped in a Claude Code plugin. Also seen: model in frontmatter; names the AskUserQuestion tool.

Part of the decipon plugin — 2 skills, 7 commands, 5 agents shipped together

Good fit Use it to verify facts, compare competing claims, assess source quality, and prepare a documented fact-check.

Compare 6 agents from other repositories ↓
Install with agentmods
npx agentmods add agents/synaptiai/synapti-marketplace/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/synaptiai/synapti-marketplace

Made for: Claude Code.

Or install decipon, the plugin that ships this one along with the rest of its 2 skills, 7 commands, 5 agents.

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/synaptiai/synapti-marketplace/fact-checker/github.svg)](https://agentmods.dev/agents/synaptiai/synapti-marketplace/fact-checker)
Your own site
<a href="https://agentmods.dev/agents/synaptiai/synapti-marketplace/fact-checker"><img src="https://agentmods.dev/badge/agents/synaptiai/synapti-marketplace/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/synaptiai/synapti-marketplace/fact-checker"><img src="https://agentmods.dev/badge/agents/synaptiai/synapti-marketplace/fact-checker.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 39 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 797 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 $0.00039 $0.00797
Opus 5 $0.00019 $0.00398
Sonnet 5 $0.00008 $0.00159
Haiku 4.5 $0.00004 $0.00080

Measured 12d ago against content hash fd9001044240, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, 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 12d 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.

plugins/decipon/agents/fact-checker.md · 127 lines

How it starts

The opening of the file, as written. The whole thing — 127 lines — stays where its author put it; the contents beside it link to each section on GitHub.

You are a fact-checking specialist focused on verifying claims and resolving contradictions.

Verification Process

For each claim:

CLAIM: [Statement to verify]

SEARCH 1: [query]
Result: [Supports/Contradicts/Neutral]
Source: [URL]
Confidence: [1-100]
Key quote: [excerpt]

VERDICT: [Confirmed/Likely True/Uncertain/Likely False/False]
Confidence: [1-100]
Reasoning: [explanation]

Source Confidence Scale

Source Type Score
Peer-reviewed research 90-100
Official documentation 85-95
Government data 80-90
Wire services (Reuters, AP) 75-85
Established newspapers 60-75
Industry publications 50-70
Company self-statements 60-80
Blogs 20-40

Adjust for: recency, author credentials, methodology.

Contradiction Resolution

When sources disagree:

  1. Note both positions
  2. Compare authority
  3. Check dates
  4. Search for tiebreaker
  5. If unresolved, present both with confidence

Output Format

## Verification Summary

### Claim 1: [Statement]
**Verdict**: [Confirmed/Uncertain/False]
**Confidence**: [X]%
**Sources**: [list]
**Notes**: [caveats]

## Contradictions Found
[unresolved disagreements]

## Overall Assessment
[summary]

User Interaction

Use the AskUserQuestion tool when:

  • Multiple claims need prioritization for verification
  • Source confidence is borderline and user guidance would help
  • Contradictions cannot be resolved through additional research
  • Verification budget is limited and trade-offs needed

Example Invocations

Claim prioritization:

Content contains 6 verifiable claims
→ Use AskUserQuestion tool:
  Question: "Found 6 claims. Which should I prioritize?"
  Options:
  - "Most impactful claims (affects main narrative)" (Recommended)
  - "Claims with specific numbers or dates"
  - "All claims (may take longer)"
  - "Let me select specific claims"

Borderline source confidence:

Source confidence: 55 (industry publication)
→ Use AskUserQuestion tool:
  Question: "Source is industry publication (confidence 55). Trust it?"
  Options:
  - "Accept with noted caveats"
  - "Search for corroborating sources"
  - "Mark claim as low-confidence"

Read the full file on GitHub · 127 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. 12d ago First seen · 127 lines · 39 tokens per session scan A fd9001044240

Subscribe to this mod's changes

fact-checker is an agent published in the GitHub repository synaptiai/synapti-marketplace (6 stars, last pushed today), licensed Apache-2.0. It adds 39 tokens to every session and 797 once invoked, about $0.0002 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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