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Skill libraries

Observation date: October 27, 2026. Release numbers, skill counts, and install paths are dated snapshots, including those labeled Verified.

A skill library is a collection of SKILL.md packages you select, install, and adapt. It does not enforce a development sequence. Superpowers adds a mandatory methodology; Orchestrating Modes select skills based on the request. See Distribution and Governance for installation, versioning, and controls.

This page compares four libraries covered in the research pass: mattpocock/skills, addyosmani/agent-skills, anthropics/skills, and vercel-labs/agent-skills. Two other collections appear on the watchlist.

At a glance

Library Maintainer Philosophy Latest release License
mattpocock/skills Matt Pocock Composable — small, independently selectable practices v1.3.1 MIT
addyosmani/agent-skills Addy Osmani Lifecycle-mapped — define → plan → build → verify → review → ship v0.6.13 Reported as open source in repository docs; per-license text not re-verified this pass
anthropics/skills Anthropic Reference implementation and demonstration material Unversioned reference repo (no single semver release tracked) Mixed — Apache-2.0 for most skills; docx, pdf, pptx, xlsx are source-available, not open source
vercel-labs/agent-skills Vercel Domain-specific — Vercel/React/Next.js/React Native audits and writing-handbook checks Unversioned at time of observation; distributed via npx skills add vercel-labs/agent-skills MIT (per repository badge)

vercel-labs/skills is the CLI behind skills.sh, not a skill collection. Vercel maintains both repositories, but one installs skills and the other supplies them.

Composition

  • mattpocock/skills ships in three buckets: engineering (TDD, code review, implementation, research, debugging, domain modeling, architecture, prototyping, specifications, tickets, triage, merge conflicts), productivity (alignment interviews, handoffs, teaching, questionnaires, writing for agents), and repository setup (issue tracking, pre-commit configuration, skill-specific guardrails via /setup-matt-pocock-skills). Skills graduate from staging into the engineering bucket as they mature — implement-spec, pr, and retro graduated in v1.3.1.
  • addyosmani/agent-skills ships 25 skills, installable individually or as a set, organized around nine slash commands (/spec, /plan, /build, /test, /review, /ship, plus /constraints, /webperf, /code-simplify). Several skills auto-activate on detected activity — designing an API triggers api-and-interface-design; building UI triggers frontend-ui-engineering.
  • anthropics/skills provides example skills, a starter template, a specification directory, and document-handling skills (docx, pdf, pptx, xlsx) distributed as a Claude Code plugin. It is explicitly demonstration and educational material, not a production content catalog.
  • vercel-labs/agent-skills is narrowly scoped to Vercel's own domain: vercel-optimize (cost/performance/reliability audits using Vercel's observability metrics), react-best-practices (40+ rules across 8 categories), web-design-guidelines (100+ accessibility/UX rules), writing-guidelines (80+ rules from Vercel's writing handbook), and react-native-guidelines (16 rules across 7 sections).

Lifecycle coverage

Of these four libraries, only addyosmani/agent-skills maps skills to lifecycle stages. mattpocock/skills and vercel-labs/agent-skills let you select practices independently. anthropics/skills supplies reference examples rather than a workflow.

Lifecycle mapping does not enforce a sequence. addyosmani/agent-skills documents /build auto as an automation shortcut, but you can invoke /build without running /spec first. Superpowers prescribes a sequence instead.

Evaluation

Quality evidence is vendor-reported; no independent third-party audits were found for these four libraries in this pass:

  • mattpocock/skills release notes describe fixed issues and graduated skills but no systematic test-suite results.
  • addyosmani/agent-skills v0.6.13 release notes cite specific fixes (broken code samples, a test-driven-development false-negative on pasted code) — concrete, but still self-reported.
  • anthropics/skills is framed as educational; Anthropic does not claim production-grade evaluation of the examples.
  • vercel-labs/agent-skills rules are sourced from "Vercel Engineering" practice documents; no external validation was found for this pass.

Treat every "N rules" or "N/N passed" figure in this section as Reported, not Verified — see Research Methodology.

Portability

All four target the Agent Skills SKILL.md format, which parses across any compliant runtime. Behavioral portability is narrower:

  • mattpocock/skills and addyosmani/agent-skills both ship through multiple native plugin marketplaces (Claude Code, Copilot, and for mattpocock/skills, Codex) in addition to the vendor-neutral npx skills@latest add ... path.
  • vercel-labs/agent-skills is installed exclusively through the skills CLI (npx skills add vercel-labs/agent-skills); no native-marketplace listing was found this pass.
  • anthropics/skills installs as a Claude Code plugin; cross-runtime install paths are not its focus.

A prior compatibility pass found basic content worked across all 18 compared agents, but support for hooks and context: fork was much narrower. See State of the Skills Market. Check the features each installed skill needs, regardless of its library.

Maintenance

  • mattpocock/skills: active, versioned releases with a visible staging-to-graduation process for new skills.
  • addyosmani/agent-skills: active, with release notes describing specific bug fixes as well as feature additions.
  • anthropics/skills: maintained as reference material; update cadence is tied to the specification and Claude Code plugin ecosystem rather than a standalone release train.
  • vercel-labs/agent-skills: maintained alongside Vercel's own engineering practice documents; no public changelog was found this pass.

Licensing and provenance

Licensing is not uniform even within a single repository. anthropics/skills is the clearest example: most skills are Apache-2.0, but docx, pdf, pptx, and xlsx are source-available rather than open source. mattpocock/skills and vercel-labs/agent-skills are MIT. addyosmani/agent-skills's precise license text per skill was not re-verified this pass.

None of the four libraries provide cryptographic signing, attestation, or lockfile-style pinning for any install path — a gap shared across the entire skills layer (see Distribution and Governance).

Dependency completeness

addyosmani/agent-skills documents an incomplete-install problem in issue #361. A per-skill npx skills add install copies skills/<name>/ but omits the repository-level references/ directory. Shared checklists can go missing without a whole-repo integration. Check dependencies when installing individual skills from any library with shared references.

Distribution

Library Native marketplace CLI-vendored Notes
mattpocock/skills Claude Code, Copilot, Codex npx skills@latest add mattpocock/skills Warns against installing both paths for one agent — duplicates every skill
addyosmani/agent-skills Claude Code npx skills add addyosmani/agent-skills Also documents a Cursor setup (.cursor/skills/ plus .cursor/rules/*.mdc) and an Antigravity CLI path
anthropics/skills Claude Code Manual clone/reference Positioned as reference material, not a general install target
vercel-labs/agent-skills None found this pass npx skills add vercel-labs/agent-skills CLI-only distribution as observed

Strengths and limitations

Library Strengths Limitations
mattpocock/skills Broadest general-engineering scope; explicit composable philosophy; widest marketplace reach (three native channels) No lifecycle structure if you want one; skill counts on main were not re-verified this pass
addyosmani/agent-skills Clearest lifecycle mapping of the four; active bug-fix-driven maintenance; auto-activation on detected task type Documented dependency-completeness gap (issue #361); narrower marketplace reach than mattpocock/skills
anthropics/skills Canonical reference for the specification; useful templates and starter examples Mixed licensing within one repo; explicitly not production-audited; not meant as a general-purpose catalog
vercel-labs/agent-skills Focused Vercel, React, Next.js, React Native, and writing guidance Single-vendor domain scope; no native-marketplace listing; no public changelog found this pass

Watchlist collections

  • numman-ali/openskills was last observed with no pushes after January 18, 2026 and conflicting license metadata and README badge. It was not re-checked this pass; verify maintenance and licensing before use.
  • github/awesome-copilot is a GitHub-owned curated channel (agents, instructions, skills, plugins, cookbook content) with a pre-registered Copilot marketplace listing. GitHub explicitly distinguishes the channel's official status from its community-sourced content — treat it as strong Copilot integration with limited cross-runtime portability, not a vetted content library.