Agent skills became a standard faster than most formats do. A directory, a SKILL.md, and since late 2025 every major harness reads the same thing. Claude Code, Codex, Cursor, Gemini CLI and Antigravity all understand the format.
What none of them agree on is where the directory goes. ~/.claude/skills, ~/.codex/skills, ~/.cursor/skills, and so on. Use more than one harness, which most of us do now, and you are either symlinking by hand or keeping copies in sync and losing.
So this is two things: four skills worth having, and an installer that puts them wherever they need to go.
npx github:catidegla/skillbelt add --all
That detects which harnesses are on your machine and installs into each. No clone, no npm install, no dependencies.
The skills
i18n-parity is the one I use most and have not seen elsewhere. It compares translation files across locales and reports keys present in one and missing in another, before the missing key ships as a blank string in production. I write bilingual software, French and English, and this class of bug is invisible in review because the reviewer reads one locale.
laravel-security-review and nextjs-security-review encode the checks I would do by hand on a diff: mass assignment, unvalidated file uploads, server actions missing authorisation, environment variables crossing into a client bundle.
secrets-audit looks for credentials committed where they should not be, with attention to the shapes that get missed because they do not look like an AWS key.
The description rule
There is a validator, and its most important rule is about the description field. It has to say when to use the skill, not only what it is.
That description is the only text an agent sees when deciding whether to load a skill. So "use when reviewing a diff, a pull request, or a controller" pulls its weight, and "a skill for Laravel security" does not.
Where this sits
The installer half is not a novel idea. agent-install does the same job and also handles MCP servers and AGENTS.md, and the skills package is building a general registry for the format. For a package manager for skills, use one of those.
What is here is a curated set of four maintained together and validated as a suite, with installation attached.
# Just one skill, just one harness
npx github:catidegla/skillbelt add i18n-parity --harness claude
# See where everything would go first
npx github:catidegla/skillbelt doctor
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