fact-checker

fact-checker is a skill for Claude Code from faizanmohiuddin482/bullpen. It costs 178 tokens per session (1,353 once invoked), scanned A, a copy of fact-checker, MIT.

A set of rules for checking external names before using them in code. It verifies that libraries, functions, configuration keys, package versions, command-line options, environment variables, and endpoints actually exist.

In plain words
What is it for?
It helps confirm third-party functions, package details, configuration options, command-line flags, environment variables, endpoints, and project helpers before they are used.
Why use it?
It prevents errors caused by inventing or misremembering an API name or setting. That can avoid failed builds and debugging time.

Skill for Claude Code

Written for Claude Code: argument-hint in frontmatter.

Part of the bullpen plugin — 10 skills shipped together

Good fit It helps confirm third-party functions, package details, configuration options, command-line flags, environment variables, endpoints, and project helpers before they are used.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/faizanmohiuddin482/bullpen/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.

Any agent
npx skills add faizanmohiuddin482/bullpen --skill fact-checker
Clone the repo
git clone --depth 1 https://github.com/faizanmohiuddin482/bullpen

Made for: Claude Code.

Or install bullpen, the plugin that ships this one along with the rest of its 10 skills.

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/skills/faizanmohiuddin482/bullpen/fact-checker/github.svg)](https://agentmods.dev/skills/faizanmohiuddin482/bullpen/fact-checker)
Your own site
<a href="https://agentmods.dev/skills/faizanmohiuddin482/bullpen/fact-checker"><img src="https://agentmods.dev/badge/skills/faizanmohiuddin482/bullpen/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/skills/faizanmohiuddin482/bullpen/fact-checker"><img src="https://agentmods.dev/badge/skills/faizanmohiuddin482/bullpen/fact-checker.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 178 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,353 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 100% copy Near-identical to another mod 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 $0.00178 $0.01353
Opus 5 $0.00089 $0.00677
Sonnet 5 $0.00036 $0.00271
Haiku 4.5 $0.00018 $0.00135

Measured 11d ago against content hash 7fb5cdbe26f7, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, 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 11d 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.

Origin

This is a copy

100% identical to fact-checker — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

skills/fact-checker/SKILL.md · 112 lines

How it starts

The opening of the file, as written. The whole thing — 112 lines — stays where its author put it; the contents beside it link to each section on GitHub.

The Fact-Checker

You are the pedant on the team who has never invented an API in his life. Where everyone else types the method name they're pretty sure exists and runs it, you open the source and read the signature first — every time, without apology. You'd rather spend ten seconds confirming than an hour debugging a name that was never real.

A plausible name is not a real name. The compiler doesn't care what you meant.

When it fires

Not every line has a fact to check. for, if, map, String.length — you know those cold, and stopping to "verify" them is theater. The check fires the moment you reach for a symbol you can't swear is real:

  • a library function, method, or class from a third-party package
  • a config key, option name, or default you're recalling from memory
  • a package version, a CLI flag, an env var, an endpoint path
  • a helper, constant, or type you assume the codebase already has
  • anything you'd write because it fits the shape you want, not because you saw it

No external symbol in the line → nothing to check. Write it and move on. YAGNI applies to paranoia too.

The move

Before the call ships, confirm the symbol exists — don't trust the memory that supplied it:

  1. Grep the codebase. The helper you're about to call — does it exist, and is its signature what you assumed? grep -rn "functionName" beats faith.
  2. Read the installed package. Open node_modules / the venv / the source. Check the real export and its arguments, not the one your memory reconstructed.
  3. Check the lockfile before you cite a version or flag. The version installed is the truth; the version you remember is a guess.
  4. When memory and the repo disagree, the repo wins. Every time. Your training is a prior, not a source.
  5. Can't verify it? Say so. Write the line and mark it unverified rather than assert a fiction with confidence.

Every check is specific to the symbol in front of you. One confirmed call beats ten elegant ones you imagined.

Read the full file on GitHub · 112 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. 11d ago First seen · 112 lines · 178 tokens per session scan A 7fb5cdbe26f7

Subscribe to this mod's changes

fact-checker is a skill published in the GitHub repository faizanmohiuddin482/bullpen (3 stars, last pushed 1mo ago), licensed MIT. It adds 178 tokens to every session and 1,353 once invoked, about $0.0009 per session on Opus 5. A static security scan graded it A with 0 findings. It is 100% identical to fact-checker, differing in 0 lines, and is treated as a copy.

Related

Other skills, from other repositories

recipe-reverse-engineer

Generate PRD and Design Docs from existing codebase through discovery, generation, verification, and review workflow.

shinpr/claude-code-workflows · 26 tokens

recipe-front-review

Reviews completed frontend implementation for governing-source compliance, scope economy, repository quality, and security, then applies user-approved React corrections.

shinpr/claude-code-workflows · 29 tokens

new-skill

Scaffold a new brooks-lint analysis skill so it passes npm run validate and npm run evals on the first try — generates skills/{name}/SKILL.md (with the mandatory "Do NOT trigger for:" clause and a Process section citing guide step ranges) plus skills/{name}/{name}-guide.md (sequentially numbered steps), then appends…

hyhmrright/brooks-lint · 145 tokens

brooks-sweep

Full-sweep mode: runs a unified analysis across all quality dimensions — code decay, architecture, tech debt, and test quality — then applies fixes directly to the codebase. Safe changes are auto-applied; risky changes are confirmed before execution. Drawing on twelve classic engineering books. Triggers when: user…

hyhmrright/brooks-lint · 178 tokens

documentation-criteria

Determines which of PRD, ADR, UI Spec, Design Doc, and Work Plan a change requires, and where each is stored. Use when deciding documentation scope, or when creating or reviewing a technical document.

shinpr/claude-code-workflows · 47 tokens

typescript-rules

React/TypeScript frontend development rules including type safety, component design, state management, and error handling. Use when implementing React components, TypeScript code, or frontend features.

shinpr/claude-code-workflows · 39 tokens