Lesson 19 / 26

A Review Checklist Before Installing or Merging a Skill

Read what a skill will make Claude do before trusting it.

Read every file, especially scripts and allowed-tools

Before installing a skill from outside your team, or merging one in a pull request, read everything: SKILL.md (what does it instruct, and does it match its description?), every script (what does it read, write, delete or send over the network?), the allowed-tools list (is it narrow?), and referenced URLs and downloads. Warning signs: instructions to disable safety checks or ignore other rules; requests for secrets or tokens; commands that download and run code; scripts that touch files outside the skill's purpose; obfuscated or encoded text; descriptions that claim one thing while the body does another; and broad pre-approved tools. Prefer skills from sources you can verify, with visible history and maintainers, pin to a specific commit or version, and run unfamiliar skills first in a sandbox or container with no credentials. If something seems off, do not install it.

Skill review checklist

Use it for any skill you did not write.

[ ] source verifiable (maintainer, history); pinned to a commit/version
[ ] SKILL.md read in full: does the body match the description?
[ ] every script read: what does it read / write / delete / send?
[ ] allowed-tools narrow (specific script, read-only where possible)
[ ] no download-and-execute, no obfuscated or encoded blobs
[ ] no requests for secrets, tokens, or to disable checks
[ ] referenced URLs and files all legitimate and necessary
[ ] first run in a sandbox / container with no credentials

Run unfamiliar skills in a sandbox first

A container with no credentials limits the damage if something is wrong.

Quick check: Which finding should make you refuse a skill?

  • A template file
  • A clear README
  • A short description
  • A setup step that downloads a remote script and pipes it to a shell
Answer

A setup step that downloads a remote script and pipes it to a shell — Download-and-execute gives the source full control of your machine.