Cuttlefish.MD Skills Library Puts 2,806 License-Checked Agent Skills to Work
There are thousands of agent skills on GitHub, and most developers find them the same way: a tweet, a star count and a leap of faith. You can't tell what a skill does without reading its SKILL.md, you often can't tell whether its license lets you reuse it, and a skill you didn't read is someone else's instructions running with your agent's permissions.
Project Cuttlefish.MD is HackerNoon's answer. It's a library of 2,908 SKILL.md files you can read in full on hackernoon.com, each credited to its author, with the license checked one repo at a time. The companion GitHub repo, hackernoon/cuttlefish-agent-skills, packages the 2,806 skills whose licenses allow redistribution into nine category plugins you can install with one command.
This guide covers how to install it in Claude Code, Codex CLI, Cursor and Gemini CLI, what's in each plugin, how the licensing works, and 21 skills worth trying first.
Why a Cuttlefish?
A cuttlefish studies its surroundings and changes its color and texture to match. A good SKILL.md does the same thing for an agent: it adapts a general-purpose model to one habitat, whether that's your codebase, your blog or your data warehouse. Cuttlefish.MD is meant to let you and your agent borrow that adaptation from any ocean.
What an Agent Skill Is
An agent skill is a folder containing a SKILL.md file (a name, a one-line description and instructions) plus any scripts, templates or reference files it needs. The agent reads only the names and descriptions up front. When a task matches a description, it loads the full instructions. That's why you can install hundreds of skills without filling the context window: unused skills cost a line each.
The format is an open standard at agentskills.io, so the same folder works across agents. For the craft of writing one, HackerNoon has published How to Write an Agent Skill, The Right Way to Write an Agent Skill and Read This Before You Write Another Agent Skill.
Install It
Claude Code. Add the marketplace once, then install the categories you want:
/plugin marketplace add hackernoon/cuttlefish-agent-skills /plugin install dev-workflow@cuttlefish Run /plugin to browse the other categories. To install everything:
/plugin install hackernoon-originals@cuttlefish /plugin install dev-workflow@cuttlefish /plugin install writing-blogging@cuttlefish /plugin install design-ui@cuttlefish /plugin install marketing-seo@cuttlefish /plugin install qa-testing@cuttlefish /plugin install security@cuttlefish /plugin install data-science@cuttlefish /plugin install learn-tech@cuttlefish Codex CLI, Cursor, Gemini CLI and other Agent Skills tools. Clone the repo and copy a category's skill folders into your agent's skills directory:
git clone https://github.com/hackernoon/cuttlefish-agent-skills cp -r cuttlefish-agent-skills/plugins/writing-blogging/skills/* your-project/.agents/skills/ Codex reads .agents/skills/ inside a project, or ~/.agents/skills/ for every project. Other tools name their own skills folder in their docs. The files work unchanged.
No install at all. Every skill can be read and copied by hand from the library on hackernoon.com. Each skill has its own page, like hackernoon.com/skills/anthropics-mcp-builder, with the full SKILL.md text.
What's in the Nine Plugins
- Writing & Blogging (706 skills): Drafting, editing, SEO-aware blogging, docs and research writing
- Data & Science (599 skills): Data analysis plus GPTomics' large bioinformatics collection
- Dev Workflow (530 skills): Planning, debugging, code review, git, deploys and agent tooling
- QA & Testing (422 skills): Playwright, unit and integration testing, QA agents
- Marketing & SEO (307 skills): Copy, launches, SEO and AI search visibility
- Design & UI (131 skills): Frontend design, native UI, design review
- Security (102 skills): Code audits, threat models, supply chain and agent guardrails
- Learn Tech (8 skills): Skills that teach you while the agent works
- HackerNoon Originals (1 skill): Skills written by HackerNoon, with more on the way
The skills come from 29 authors. The biggest contributors are Daniel Avila's Claude Code Templates, GPTomics, Pramod Dutta's QASkills, Microsoft, Kostja's marketing skills, Seth Hobson's agents collection, Tech Leads Club, Daniel Agrici, Garry Tan's gstack and Corey Haines, alongside official skills from Anthropic, Sentry, Cloudflare, Stripe, Supabase, Expo, Snyk, Vercel Labs and CodeRabbit, and individual developers including Matt Pocock, Addy Osmani, Jesse Vincent, Thomas Ricouard, Matteo Collina and Anthony Fu.
How the Licensing Works
This is the part that makes Cuttlefish different from a scraped "awesome list."
- Copied in: skills licensed MIT, Apache 2.0, BSD or CC-BY are republished unchanged, each with its license file and an
ATTRIBUTION.mdnaming the author, the source repo and the exact commit it came from. - Judged per skill: a skill's own license overrides its repo's, so each skill is checked individually.
- Link-only: unlicensed or "all rights reserved" skills stay on hackernoon.com, linked to their authors, and are never copied into the repo. They're logged in
skipped.jsonwith the reason, alongside skills that moved upstream or had no description.
That's why the library on hackernoon.com lists 2,908 skills while the installable repo holds 2,806. Every skill's author, source, commit and license is listed in catalog.json. Authors who want a skill removed, recategorized or updated can open an issue or email support@hackernoon.com.
21 Skills to Try First
One or two picks from each plugin, chosen for how quickly they change what your agent does.
Dev Workflow
530 skills for the daily loop of planning, building, debugging and shipping.
1. ship
By Garry Tan · MIT · Dev Workflow plugin
From Y Combinator's Garry Tan and his gstack suite: merge the base branch, run the tests, review the diff, bump the version and changelog, push and open a pull request, in one command. gstack has 59 skills in the library, including CEO-, design- and engineering-style plan reviews.
Read the full SKILL.md on HackerNoon · Source on GitHub
2. office-hours
By Garry Tan · MIT · Dev Workflow plugin
YC-style office hours for your idea or plan, from the same suite. A good stress test before you spend a week building the wrong thing.
Read the full SKILL.md on HackerNoon · Source on GitHub
3. systematic-debugging
By Jesse Vincent (obra) · MIT · Dev Workflow plugin
From Jesse Vincent's Superpowers: when anything breaks, find the root cause before proposing a fix. It stops the agent's favorite habit of patching symptoms until the test turns green.
Read the full SKILL.md on HackerNoon · Source on GitHub
4. spec-driven-development
By Addy Osmani · MIT · Dev Workflow plugin
Addy Osmani's skill writes the spec before the code: objectives, scope and a breakdown of independently testable capabilities. It kicks in when requirements are vague, which is most of the time.
Read the full SKILL.md on HackerNoon · Source on GitHub
5. grilling
By Matt Pocock (Total TypeScript) · MIT · Dev Workflow plugin
Matt Pocock's skill makes the agent interview you relentlessly about a plan or decision until the weak spots show. Uncomfortable and useful.
Read the full SKILL.md on HackerNoon · Source on GitHub
Writing & Blogging
706 skills for drafting, editing and publishing.
6. blog-factcheck
By Daniel Agrici · MIT · Writing & Blogging plugin
Fetches every source a post cites and checks that the claimed number or quote is really there, marking uncited claims as unverified. The single best guard against AI-invented statistics.
Read the full SKILL.md on HackerNoon · Source on GitHub
7. humanizer
By Daniel Avila · MIT · Writing & Blogging plugin
Strips the patterns readers associate with AI writing, based on Wikipedia's "Signs of AI writing" guide: inflated language, vague attributions, em-dash overuse and the rest.
Read the full SKILL.md on HackerNoon · Source on GitHub
Design & UI
131 skills for interfaces that don't look generated.
8. frontend-design
By Anthropic · Apache-2.0 · Design & UI plugin
Anthropic's design-lead skill names the clichés of AI-generated pages (the cream background with a terracotta accent, the identical rounded cards, the all-caps eyebrow labels) and makes the agent plan a distinctive direction before writing any CSS.
Read the full SKILL.md on HackerNoon · Source on GitHub
9. design-review
By Garry Tan · MIT · Design & UI plugin
A designer's-eye QA pass from gstack that finds inconsistent spacing, hierarchy problems, AI-slop patterns and slow interactions, then fixes them.
Read the full SKILL.md on HackerNoon · Source on GitHub
10. swiftui-liquid-glass
By Thomas Ricouard · MIT · Design & UI plugin
Thomas Ricouard's skill for adopting Apple's Liquid Glass API in SwiftUI on iOS 26 and later, or reviewing an existing implementation for correctness, performance and design fit.
Read the full SKILL.md on HackerNoon · Source on GitHub
Marketing & SEO
307 skills for getting the thing you built in front of people.
11. ai-seo
By Corey Haines · MIT · Marketing & SEO plugin
Corey Haines' 5,000-word guide to showing up in AI answers: answer engine optimization, llms.txt and agent-readable sites.
Read the full SKILL.md on HackerNoon · Source on GitHub
12. launch
By Corey Haines · MIT · Marketing & SEO plugin
Plans a product launch or feature announcement end to end, from waitlist and early access through Product Hunt, changelog and pre-launch QA.
Read the full SKILL.md on HackerNoon · Source on GitHub
QA & Testing
422 skills, most of them from Pramod Dutta's QASkills, plus official picks from Anthropic and Vercel Labs.
13. webapp-testing
By Anthropic · Apache-2.0 · QA & Testing plugin
Anthropic's Playwright skill for testing local web apps, with a helper that starts your servers and a decision tree for static versus dynamic pages.
Read the full SKILL.md on HackerNoon · Source on GitHub
14. agent-browser
By Vercel Labs · Apache-2.0 · QA & Testing plugin
Vercel Labs' browser automation CLI for agents: navigate, fill forms, click, screenshot and extract data.
Read the full SKILL.md on HackerNoon · Source on GitHub
15. qa-agent-claude
By Pramod Dutta · MIT · QA & Testing plugin
Turns Claude Code into an autonomous QA loop that maps your app, writes tests for real user journeys, runs them, repairs broken locators and reports coverage.
Read the full SKILL.md on HackerNoon · Source on GitHub
Security
102 skills for auditing what your agent writes and limiting what it can do.
16. secure-at-inception
By Snyk · Apache-2.0 · Security plugin
Scans every change the agent makes and reports only the new issues it introduced. Requires a Snyk account and the Snyk MCP server.
Read the full SKILL.md on HackerNoon · Source on GitHub
17. skill-scanner
By Sentry · Apache-2.0 · Dev Workflow plugin
Audits other skills for prompt injection, malicious scripts, excessive permissions and leaked secrets before you install them. Use it on anything you find outside a vetted library, including this one.
Read the full SKILL.md on HackerNoon · Source on GitHub
Data & Science
599 skills, including more than 550 bioinformatics skills from GPTomics.
18. polars
By Daniel Avila · MIT · Writing & Blogging plugin
Teaches the agent Polars, the fast Arrow-based DataFrame library, so it stops reaching for pandas by default on large files.
Read the full SKILL.md on HackerNoon · Source on GitHub
19. statistical-analysis
By Daniel Avila · MIT · Writing & Blogging plugin
Picks the right test, checks its assumptions and reports effect sizes and confidence intervals, not just a p-value.
Read the full SKILL.md on HackerNoon · Source on GitHub
Learn Tech
The smallest plugin, and the most underrated: skills that make you better instead of just making the agent faster.
20. learning-opportunities
By Tech Leads Club · MIT · Learn Tech plugin
After the agent finishes architectural work like new files or schema changes, it offers short interactive exercises so you understand what was built. A good antidote to shipping code you can't explain.
Read the full SKILL.md on HackerNoon · Source on GitHub
21. teach
By Matt Pocock (Total TypeScript) · MIT · Learn Tech plugin
Matt Pocock's skill turns the agent into a tutor for a new concept, inside your own workspace.
Read the full SKILL.md on HackerNoon · Source on GitHub
HackerNoon Originals
The first skill written by HackerNoon is pixel-icon-library, which installs and uses HackerNoon's open-source Pixel Icon Library, the pixel-art icon set on a 24px grid that HackerNoon itself is drawn with, available as an icon font, React component or raw SVG.
Two more are in progress: write-for-hackernoon, which drafts, self-edits and submits against the HackerNoon Editing Protocol, and tech-blogging, with headline and structure patterns drawn from more than 150,000 HackerNoon stories.
Frequently Asked Questions
Will installing a whole plugin slow my agent down? Not meaningfully. Agents load only each skill's name and description until a task matches, so an unused skill costs about a line of context. Installing a few targeted plugins is still tidier than installing all nine.
Are these skills safe? Each one is republished unchanged from its source commit, with attribution, so you can compare it with the original. Licensing is checked, but a license isn't a security review. Read a skill before you rely on it, and consider running Sentry's skill-scanner first.
Can I suggest a skill or a source repo? More source repos are being added. Watch or star the repo to follow along, and email support@hackernoon.com with suggestions.
I'm a skill author. How do I update or remove my skill? Open an issue on the repo or email support@hackernoon.com.
Start Here
/plugin marketplace add hackernoon/cuttlefish-agent-skills /plugin install design-ui@cuttlefish /plugin install dev-workflow@cuttlefish /plugin install learn-tech@cuttlefish /plugin install marketing-seo@cuttlefish /plugin install qa-testing@cuttlefish /plugin install security@cuttlefish /plugin install writing-blogging@cuttlefish Read every skill in full at Project Cuttlefish.MD. And if the library saves you an afternoon of GitHub digging, star hackernoon/cuttlefish-agent-skills. Stars help other developers find it and tell us which oceans to explore next.