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SkillClaude Code logoClaude CodeCodex logoCodexCursor logoCursorCoding Agent SkillsVerified

system-design-skills: design systems by reasoning, not memorising

22 building-block skills plus a /design command that walk your agent through a system design the way a strong engineer does: pin down requirements, size it with real numbers, pick parts like caches, queues and databases, explain each trade-off, test how it fails, then save a scored design doc and diagram.

In short: 22 building-block skills plus a /design command that walk your agent through a system design the way a strong engineer does: pin down requirements, size it with real numbers, pick parts like caches, queues and databases, explain each trade-off, test how it fails, then save a scored design doc and diagram. It is a free skill for people who use Claude Code, Codex or Cursor and want help with coding agent skills.

Checked on · Added

Open on GitHub · ★ 104

Works with

Agent / toolAccess / costLink
Claude CodePaid Claude plan or APIclaude.com/claude-code
CodexChatGPT plan or APIopenai.com/codex
CursorFree tier + paidcursor.com
GitHub repoOpen source · ★ 104proyecto26/system-design-skills

Try it in 60 seconds

/plugin marketplace add proyecto26/system-design-skills   # Claude Code, then: /plugin install system-design-skills
npx skills add proyecto26/system-design-skills   # Codex, Cursor and others
codex plugin marketplace add proyecto26/system-design-skills   # Codex plugin, then: codex plugin add system-design-skills@system-design-skills-marketplace

Install command copied from the project README. Check the README for the latest version.

What it does

22 building-block skills plus a /design command that walk your agent through a system design the way a strong engineer does: pin down requirements, size it with real numbers, pick parts like caches, queues and databases, explain each trade-off, test how it fails, then save a scored design doc and diagram.

One skill per part of a system (requirements, back-of-the-envelope sizing, DNS, load balancing, CDN, API design, storage, caching, queues, scheduling, consistency, resilience, observability, scaling and more), each with…

Short excerpt from the README of proyecto26/system-design-skills. Read the full README on GitHub.

Inside the repo

At a glanceQuick StartInstallationStandardsYour first designThe three ways to use itBuilding blocksUsage examplesProvider modularityHow it worksRunning the evalsProject structure

A prompt to try

/design a URL shortener for 50 million links a month with click stats. Start by asking me what matters most, size it with numbers, and list the trade-offs.

Written by us so you can reuse it. Replace each [bracket] with your details.

Step by step

  1. Open the GitHub repo and read the "At a glance" map of the 22 skills.
  2. Claude Code: /plugin marketplace add proyecto26/system-design-skills, then /plugin install system-design-skills. Codex and others: npx skills add proyecto26/system-design-skills.
  3. In Claude Code type /design and describe what you want to build; in Codex say "use the system-design skill to design ...".
  4. Answer its scoping questions, then read the trade-offs and failure section before you accept the design.

Watch out for

It is a thinking aid, not a code generator: the output is a design doc and an HTML/SVG diagram in docs/design/. The /design command and orchestrator agent only exist in Claude Code; in Codex you call the skills by name. The plugin marketplace clones over SSH, so use the https URL if you have no GitHub SSH key.

Docs, demos & materials

Common questions

What does system-design-skills do?

22 building-block skills plus a /design command that walk your agent through a system design the way a strong engineer does: pin down requirements, size it with real numbers, pick parts like caches, queues and databases, explain each trade-off, test how it fails, then save a scored design doc and diagram.

Which AI agents can use system-design-skills?

It works with Claude Code, Codex and Cursor. The code is on GitHub at proyecto26/system-design-skills.

Is system-design-skills free?

Free & open source (MIT). Plain Markdown skills with no runtime dependencies.

How do I install system-design-skills?

Run the install command from the README: “/plugin marketplace add proyecto26/system-design-skills # Claude Code, then: /plugin install system-design-skills”. Check the README on GitHub for the latest version, then follow the steps on this page.

Is system-design-skills safe to install?

We read 177 instruction and code files in the repo and found no red flags. That is not a guarantee, so review anything that runs commands on your machine.

Sources & credit

All credit to the original authors. We rewrite in our own words and link back. Something wrong? Report it.

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