Borrowing it
Nothing to install: this file belongs to rajbos/ai-engineering-fluency. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/rajbos/ai-engineering-fluency/main/.claude/skills/check-urls/SKILL.mdgit clone --depth 1 https://github.com/rajbos/ai-engineering-fluencyWrote 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.
[](https://agentmods.dev/skills/rajbos/ai-engineering-fluency/check-urls)<a href="https://agentmods.dev/skills/rajbos/ai-engineering-fluency/check-urls"><img src="https://agentmods.dev/badge/skills/rajbos/ai-engineering-fluency/check-urls/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.
<a href="https://agentmods.dev/skills/rajbos/ai-engineering-fluency/check-urls"><img src="https://agentmods.dev/badge/skills/rajbos/ai-engineering-fluency/check-urls.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00048 | $0.00921 |
| Opus 5.5 | $0.00019 | $0.00368 |
| Sonnet 5.5 | $0.00010 | $0.00184 |
| Haiku 4.5 | $0.00005 | $0.00092 |
Grade A, and why
check-urls 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 yesterday.
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.
How it starts
The opening of the file, as written. The whole thing — 58 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Check URLs Skill
This skill scans all TypeScript source files for hardcoded http:// and https:// URLs and performs HTTP HEAD requests to verify each one resolves without a 4xx/5xx error.
When to Use This Skill
Use this skill when you need to:
- Validate links added to fluency hints or tips in
maturityScoring.ts - Check that VS Code docs URLs, tech.hub.ms video links, or any other hardcoded URLs are still live
- Audit the codebase after bulk URL changes to catch 404s before a release
- Routinely health-check external references as part of a maintenance pass
Running the Check
node .github/skills/check-urls/check-urls.js
The script will:
- Recursively scan every
*.tsfile undersrc/ - Extract all unique
https?://...URLs (strips trailing punctuation, skips template literals) - Skip, and report, every URL whose host is internal:
localhost/*.localhost, loopback (127/8,::1), link-local (169.254/16,fe80::/10), private (10/8, 172.16/12, 192.168/16,fc00::/7), carrier-grade NAT (100.64/10) or unspecified (0/8,::) — including hostnames that resolve via DNS to such an address. The resolved address is checked again when the connection is made, so a changing DNS answer cannot slip through - Send an HTTP HEAD request to each remaining URL (with a 10-second timeout)
- If HEAD returns 403, 405 or 501 — statuses that usually mean the server does not handle HEAD — retry once with GET. Any other error status is reported as-is, without a GET
- Print ✅ OK, ⚠️ REDIRECT, ⚠️ INSECURE (plain
http:), ⏭️ SKIPPED or ❌ BROKEN for every URL - Exit with code
1if any URL is broken (4xx/5xx after the rules above, timeout or connection error)
Interpreting Output
| Symbol | Meaning |
|---|---|
| ✅ OK | 2xx response — URL is live |
| ⚠️ REDIRECT | 3xx response — URL redirects; consider updating to the final destination |
| ⚠️ INSECURE | Plain http: URL — still checked, but switch it to https: where the site supports it |
| ⏭️ SKIPPED | Host is localhost or an internal/private address (directly or after DNS) — never requested |
| ❌ BROKEN | 4xx/5xx or connection failure — URL must be fixed |
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.
- yesterday First seen · 58 lines · 48 tokens per session scan A ff50287e1224
check-urls is a skill published in the GitHub repository rajbos/ai-engineering-fluency (119 stars, last pushed yesterday), licensed MIT. It adds 48 tokens to every session and 921 once invoked, about $0.0002 per session on Opus 5.5. 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 2026-10-26.
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