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Agent skill

Jakobs Law

by Owl-Listener in Owl-Listener/designer-skills

Apply Jakob's Law — users expect your product to work like the others they already use.

MITAuto-check passedFrontend & Design

Install Jakobs Law

skills CLI
$ npx skills add Owl-Listener/designer-skills --skill jakobs-law -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install Owl-Listener/designer-skills jakobs-law --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/Owl-Listener/designer-skills.git skills-src && mkdir -p .claude/skills && cp -r skills-src/interaction-design/skills/jakobs-law .claude/skills/jakobs-law && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
jakobs-law
GitHub stars
2.9k
Token cost
~999 tokens
SKILL.md length
538 words
Files
1
Skills in repo
107
Repo updated
First seen
Licence
MIT

At a glance

Apply Jakob's Law — users expect your product to work like the others they already use.

  • Works in 3 steps: Discover that the familiar pattern does… → Work out the new pattern → Hold both patterns in memory until the…
  • Deciding whether to innovate on a familiar pattern
  • SKILL.md covers What You Do, The Principle, Where Conventions Are Strongest and The Cost of Departing From…, plus 3 more sections
  • Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md

What it does

Jakobs Law is an agent skill from Owl-Listener/designer-skills. Apply Jakob's Law — users expect your product to work like the others they already use. Use when deciding whether to innovate on a familiar pattern. For OS-mandated conventions specifically, use platform-conventions (ui-design).

Its SKILL.md is about 1000 tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.

It sits in Frontend & Design, covering UI design. The repository describes itself as: Designer Skills Collection: agentic skills, commands, and plugins for design — from research to systems, UI, interaction, and delivery. The licence is MIT.

When your agent uses it

  • Deciding whether to innovate on a familiar pattern
  • Tasks that involve UI design

Example prompts

  • “/jakobs-law”

Workflow steps

3 steps, taken from the first numbered list in SKILL.md.

  1. Discover that the familiar pattern does not apply
  2. Work out the new pattern
  3. Hold both patterns in memory until the new one is learned

What it can do on your machine

Read from SKILL.md and the folder at commit 9a6930c. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    No scripts in the folder and no shell commands in SKILL.md.

    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

Jakobs Law loads about 999 tokens when it runs. Until then it costs about 60 tokens; SKILL.md has 538 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~60
When it runs · the whole SKILL.md, loaded when a task matches
~999

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

Auto-check passed

The automated check found no risky patterns in SKILL.md.

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 Owl-Listener/designer-skills at commit 9a6930c, republished under its MIT licence (© Owl-Listener). 538 words, ~999 tokens.

Download SKILL.mdSave it as .claude/skills/jakobs-law/SKILL.md (or your agent's skills folder).
name
jakobs-law
description
Apply Jakob's Law — users expect your product to work like the others they already use. Use when deciding whether to innovate on a familiar pattern. For OS-mandated conventions specifically, use `platform-conventions` (ui-design).

Jakob's Law

You are an expert in mental models, user expectations, and the role of convention in interface design.

What You Do

You apply Jakob's Law to identify which design conventions carry strong user expectations, evaluate the cost of departing from them, and make deliberate decisions about when to follow and when to innovate.

The Principle

Users spend most of their time on other products. They arrive at yours with pre-built expectations about where navigation lives, what a cart icon means, how a toggle behaves, and where to look for settings. Jakob's Law, articulated by Jakob Nielsen, states:

Users prefer your site to work the same way as all the other sites they already know.

This is not an argument for copying competitors. It is an argument for understanding which conventions carry strong enough expectations that departing from them imposes a real learning cost — and being deliberate when you do.

Where Conventions Are Strongest

Some patterns are so universal that users rely on them unconsciously:

  • Logo top-left → home: violating this forces users to hunt for a way back
  • Shopping cart icon → checkout: recognised globally across languages and cultures
  • Hamburger menu → hidden navigation: established on mobile despite early friction
  • Search icon (magnifying glass) → search field: universal; even non-technical users recognise it
  • X to close: applies to modals, tooltips, notifications, drawers
  • Blue underlined text → link: weakening but still active in text-heavy contexts

The Cost of Departing From Convention

Every time you deviate, users must:

  1. Discover that the familiar pattern does not apply
  2. Work out the new pattern
  3. Hold both patterns in memory until the new one is learned

This cost is paid on every visit until the pattern is learned — which requires repetition and motivation. The benefit of the new approach must outweigh this cumulative cost across your entire user base.

Show full SKILL.md (236 more words)Show less

When Deviation Is Justified

Departure from convention is justified when:

  • The conventional approach fails at something your use case requires
  • Your user base has a domain-specific convention that supersedes the general one (keyboard shortcuts in professional tools, for example)
  • Testing shows the conventional approach performs measurably worse for your specific task
  • You are establishing a genuinely new interaction category where no strong convention exists

Departure is not justified by:

  • Wanting to feel differentiated
  • Aesthetic preference in isolation
  • Internally developed conventions that have not been tested against real users

Applying It in Practice

  • Audit competitors before designing: how do 3–5 comparable products handle this interaction?
  • Weight by task frequency: high-frequency interactions must follow conventions; low-frequency ones have more latitude
  • Name the convention before departing from it: if you cannot articulate the existing user expectation, you have not researched it
  • Test with users who know the category: they hold the strongest prior expectations and will surface violations fastest

Best Practices

  • Start new design work by cataloguing dominant conventions in the category, not from a blank canvas
  • Flag every departure from convention in design reviews as a deliberate, reasoned choice — not a default
  • Reserve creative divergence for low-stakes or infrequent interactions; keep high-frequency, high-stakes interactions conventional
  • Onboarding cannot substitute for convention — teaching users a custom pattern is expensive and fragile
  • Return to convention when a novel pattern tests poorly; the default is almost always more efficient than the invention

© Owl-Listener, 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 interaction-design/skills/jakobs-law of Owl-Listener/designer-skills.

Open the folder on GitHubat commit 9a6930c

Compare with similar skills

Jakobs Law next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Jakobs Law compared with similar skills
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Make Interfaces Feel Bettersamuelclay/NewsBlur7.6k10 repos~1.5kAutomated safety check: PassMIT
UI UX Pro MaxZxBing0066/pixel-converter18113 repos~2.6kAutomated safety check: NotesBSD-2-Clause
Design Dnazanwei/design-dna1.9k1 repos~2.1kAutomated safety check: PassMIT

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Categories

Questions about Jakobs Law

What does Jakobs Law do?

Apply Jakob's Law — users expect your product to work like the others they already use. Jakobs Law is an agent skill from Owl-Listener/designer-skills. Apply Jakob's Law — users expect your product to work like the others they already use.

When should I use Jakobs Law?

Jakobs Law fits situations like: deciding whether to innovate on a familiar pattern; tasks that involve UI design.

How do I install Jakobs Law in Claude Code?

Run `npx skills add Owl-Listener/designer-skills --skill jakobs-law -a claude-code`. Or copy the skill folder (interaction-design/skills/jakobs-law in Owl-Listener/designer-skills) into .claude/skills/jakobs-law in your project. Claude Code loads it when a task matches its description.

How do I install Jakobs Law in Codex?

Run `npx skills add Owl-Listener/designer-skills --skill jakobs-law -a codex`. Or copy the skill folder (interaction-design/skills/jakobs-law in Owl-Listener/designer-skills) into .agents/skills/jakobs-law in your project. Codex loads it when a task matches its description.

Can I use Jakobs Law in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add Owl-Listener/designer-skills --skill jakobs-law -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/jakobs-law, .gemini/skills/jakobs-law, .github/skills/jakobs-law and .opencode/skills/jakobs-law in your project.

What does Jakobs Law need to run?

SKILL.md names no scripts, command-line tools or credentials: Jakobs Law is instructions for the agent only.

Does Jakobs Law access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is Jakobs Law safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Jakobs Law use?

Jakobs Law is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Jakobs Law use?

About 999 tokens (SKILL.md is roughly 4k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Jakobs Law?

Skills that share tags, products or a category with Jakobs Law: UI Styling (Ohh-889/skyroc, 795 stars), LobeHub Interactive Prototype (lobehub/lobehub, 83k stars), Make Interfaces Feel Better (samuelclay/NewsBlur, 7.6k stars) and UI UX Pro Max (ZxBing0066/pixel-converter, 181 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Jakobs Law?

Owl-Listener (a GitHub user) maintains it in Owl-Listener/designer-skills, which has 2,871 GitHub stars. The repository holds 107 skills in this directory. The repository was last updated on September 5, 2026.

Source: Owl-Listener/designer-skills on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.