Homebrew Cask Creator

What it does

When your agent uses it

• Adding a macOS application to Homebrew as a new cask
• Checking whether an app is suitable for homebrew-cask before investing time
• Working out the livecheck strategy and checksum for a cask

Example prompts

• “Create a Homebrew cask for the app downloadable at the URL I will paste next.”
• “Is this DMG suitable for submission to homebrew-cask?”
• “Package our internal menu bar app for Homebrew and work out how livecheck should track new versions.”

Requirements

• Homebrew on macOS
• The gh CLI and git for submission
• Network access to download the app
• Pre-approved tools (allowed-tools): Read, Grep, Glob, WebFetch, WebSearch, Bash(brew *), Bash(gh *), Bash(curl *), Bash(hdiutil *), Bash(defaults read *), Bash(shasum *), Bash(git *), Bash(plutil *), Bash(file *), Bash(lipo *), Bash(ls *), Bash(find *), Bash(strings *), Bash(unzip *), Bash(open *), Bash(${CLAUDE_PLUGIN_ROOT}/scripts/*)

Workflow steps

6 steps, taken from the step headings in SKILL.md.

1. 1Pre-flight Checks
2. 2Download and Inspect
3. 3Livecheck Strategy
4. 4Write the Cask
5. 5Testing
6. 6Submit PR

What it can do on your machine

Read from SKILL.md and the folder at commit 9cca0f4. It shows what the files ask for, not the result of running them.

• Tool permissions

  Pre-approves these tools, so the agent can use them without asking each time:

  • Read
  • Grep
  • Glob
  • WebFetch
  • WebSearch
  • Bash(brew *)
  • Bash(gh *)
  • Bash(curl *)
  • Bash(hdiutil *)
  • Bash(defaults read *)

  …and 11 more on the same allowed-tools line.

  From allowed-tools in the SKILL.md frontmatter.

• Runs code

  Shell commands in SKILL.md call:

  • brew
  • bundle

  From the folder's file list and the shell code blocks in SKILL.md.

• Network

  No URLs in SKILL.md.

  From URLs in SKILL.md, links to its own repository left out.

• Credentials

  Names no API keys, tokens, secrets or passwords.

  From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Homebrew Cask Creator loads about 1.6k tokens when it runs. Until then it costs about 80 tokens; SKILL.md has 516 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it

~80

When it runs · the whole SKILL.md, loaded when a task matches

~1.6k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from malob/nix-config at commit 9cca0f4, republished under its MIT licence (© malob). 516 words, ~1,607 tokens.

name

new-cask

description

This skill should be used when the user asks to "add a cask to homebrew", "create a homebrew cask", "add an app to homebrew", "new cask for", "homebrew cask for", "package an app for homebrew", "submit to homebrew-cask", "make a cask", "contribute a cask", or wants to package a macOS application for Homebrew.

allowed-tools

Read, Grep, Glob, WebFetch, WebSearch, Bash(brew *), Bash(gh *), Bash(curl *), Bash(hdiutil *), Bash(defaults read *), Bash(shasum *), Bash(git *), Bash(plutil *), Bash(file *), Bash(lipo *), Bash(ls *), Bash(find *), Bash(strings *), Bash(unzip *), Bash(open *), Bash(${CLAUDE_PLUGIN_ROOT}/scripts/*)

argument-hint

<url>

1. Pre-flight checks    → Agent: pre-flight-checker
2. Download & inspect   → Agent: app-inspector
3. Livecheck strategy   → Agent: livecheck-advisor
4. Write cask file      → Agent: cask-writer
5. Testing              → Automated tests, install, createzap, uninstall
6. Submit PR            → Agent: pr-submitter

Use the Task tool:
- subagent_type: homebrew:pre-flight-checker
- prompt: Check if this app is suitable for homebrew-cask submission.
  <include whatever info you have: URL, app name, homepage>

Use the Task tool:
- subagent_type: homebrew:app-inspector
- prompt: Download and inspect the app.
  Download URL: <url>
  Homepage: <homepage>

Use the Task tool:
- subagent_type: homebrew:livecheck-advisor
- prompt: Recommend a livecheck strategy for <app-name>.
  Download URL: <url>
  Homepage: <homepage>
  Update URL: <appcast-or-feed-url-if-found>
  Current version: <version>

Use the Task tool:
- subagent_type: homebrew:cask-writer
- prompt: Write a cask for <app-name> with this metadata:
  Token: <token>
  Version: <version>
  URL: <download-url>
  SHA256: <checksum> (or :no_check if unversioned URL)
  (If separate binaries per architecture, provide URL and SHA256 for each)
  Name: <display-name>
  Description: <one-line-desc>
  Homepage: <homepage>
  Bundle ID: <bundle-id>
  App bundle: <app-name>.app
  Min macOS: <min-version>
  Auto-updates: <yes/no>
  Livecheck: <livecheck-block>
  Architecture: <arm64/intel/universal, only if not universal>

${CLAUDE_PLUGIN_ROOT}/scripts/test-cask.sh "<token>"

Use the Task tool:
- subagent_type: homebrew:pr-submitter
- prompt: Submit a PR for the <token> cask.
  Version: <version>
  Cask path: <path-to-cask-file>
  All tests passed: yes

© malob, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

Just SKILL.md in configs/claude/plugins/homebrew/skills/new-cask of malob/nix-config.

Open the folder on GitHubat commit 9cca0f4