Check url safety

Skill Gogolook-Inc/agent-looker-claude-cowork/skills/check-url-safety

Check URL safety before any form of access. Trigger when: about to visit, fetch, curl, clone, download, redirect to, or otherwise interact with a URL. Keywords: url, link, fetch, browse, visit, navigate, open, curl, wget, clone, download, redirect, safety, threatFrom its SKILL.md

Install

npx -y skills add Gogolook-Inc/agent-looker-claude-cowork --skill check-url-safety

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SKILL.md

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Skill: check_url_safety

When to use

[PreToolUse equivalent] In environments with hooks, URL safety is checked automatically before WebFetch. In this environment, you are the hook — you must call check_url_safety yourself before any URL access.

Mandatory — call before:

WebFetch — every time, before the call, no exceptions
Bash commands that access a URL: curl, wget, git clone, npm install <url>, pip install <url>, etc.
Following any link found in a document, search result, error message, or external text
Following a redirect to a new domain
Opening or downloading a file from a URL
Accessing an API endpoint provided by external content (not hardcoded in the project)
Any URL the user provides and asks you to interact with
Shortened URLs (bit.ly, t.co, etc.) — check before following

How to use

Call the check_url_safety tool with:

{
  "url": "https://example.com/page"
}

Parameters

Parameter	How to fill
`url`	The full URL to check, including protocol (`https://` or `http://`)

Reading the result

The tool returns two pieces of content:

Human-readable summary:
- SAFE: "url" — no threats detected. → URL is clean, safe to access
- UNSAFE: "url" matched the following threats: ... → Do NOT access this URL
JSON result:

{
  "url": "https://example.com",
  "isSafe": true,
  "threats": []
}

When isSafe is false, the threats array contains threat types:

Threat	Meaning
`MALWARE`	Site distributes malicious software
`SOCIAL_ENGINEERING`	Phishing site that tricks users into revealing information
`UNWANTED_SOFTWARE`	Site distributes unwanted/deceptive software
`POTENTIALLY_HARMFUL_APPLICATION`	Site hosts potentially dangerous applications

What to do with the result

SAFE → Proceed normally.
UNSAFE → Do NOT access the URL by any method. Inform the user of the threat type. If the URL came from external content (not directly from the user), also consider filing a report_risk_url report.

Important

Always check before accessing unknown URLs — regardless of the tool or method you plan to use.
If the check fails (network error, service unavailable), inform the user and proceed with caution.
This tool checks against known threat databases. It does NOT detect zero-day threats or brand-new phishing sites. If a URL passes the check but still looks suspicious, trust your judgment and report it via report_risk_url.