Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add majiayu000/spellbook --skill product-ux-expertgit clone --depth 1 https://github.com/majiayu000/spellbookWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/majiayu000/spellbook/product-ux-expert)<a href="https://agentmods.dev/skills/majiayu000/spellbook/product-ux-expert"><img src="https://agentmods.dev/badge/skills/majiayu000/spellbook/product-ux-expert/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/majiayu000/spellbook/product-ux-expert"><img src="https://agentmods.dev/badge/skills/majiayu000/spellbook/product-ux-expert.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00043 | $0.03069 |
| Opus 5.5 | $0.00017 | $0.01228 |
| Sonnet 5.5 | $0.00009 | $0.00614 |
| Haiku 4.5 | $0.00004 | $0.00307 |
Grade A, and why
product-ux-expert scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2mo ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 450 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Product UX Expert
Core Principles
- Reduce Cognitive Load — Minimize mental effort required for every interaction
- Accessibility First — WCAG 2.2 AA is the baseline, not an afterthought
- Evidence-Based — Decisions backed by user research, not assumptions
- Anticipatory Design — Predict user needs before they ask
- Ethical Design — No dark patterns, transparent data practices
- Mobile First — Design for smallest screens, enhance for larger
Quick Reference
Nielsen's 10 Heuristics
| # | Heuristic | Key Question |
|---|---|---|
| 1 | Visibility of System Status | Does the user always know what's happening? |
| 2 | Match System & Real World | Does it use familiar language and concepts? |
| 3 | User Control & Freedom | Can users easily undo or exit? |
| 4 | Consistency & Standards | Does it follow platform conventions? |
| 5 | Error Prevention | Does it prevent errors before they occur? |
| 6 | Recognition over Recall | Is information visible, not memorized? |
| 7 | Flexibility & Efficiency | Are there shortcuts for experts? |
| 8 | Aesthetic & Minimalist Design | Is every element necessary? |
| 9 | Help Users with Errors | Are error messages helpful and actionable? |
| 10 | Help & Documentation | Is help available when needed? |
Cognitive Psychology
Cognitive Load Types
Intrinsic Load — Complexity inherent to the task itself
Extraneous Load — Unnecessary complexity from poor design (eliminate this!)
Germane Load — Mental effort for learning/understanding (support this)
Key Laws
Hick's Law — More choices = longer decision time
→ Limit options to 5-7, use progressive disclosure
Miller's Law — Working memory holds 7±2 items
→ Chunk information, use visual grouping
Fitts's Law — Larger, closer targets are easier to click
→ Make primary actions big and accessible
Jakob's Law — Users expect your site to work like others
→ Follow established patterns
Von Restorff — Different items are more memorable
→ Highlight CTAs with contrast
Serial Position — First and last items remembered best
→ Put key info at start/end of lists
What ships with it
4 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 2mo ago First seen · 450 lines · 43 tokens per session scan A d3e0b940dd71
product-ux-expert is a skill published in the GitHub repository majiayu000/spellbook (290 stars, last pushed 2d ago), licensed MIT. It adds 43 tokens to every session and 3,069 once invoked, about $0.0002 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.
product-ux-expert compared with skills from other repositories
| Mod | Type | Stars | Last push | Licence | Scan | Tokens | Works with |
|---|---|---|---|---|---|---|---|
| product-ux-expertmajiayu000/spellbook | Skill | 290 | 2d ago | MIT | A | 43 | Claude Code, Codex |
| intelligent-uievoelsewhere/evoflux | Skill | 13 | 2d ago | Apache-2.0 | A | 90 | Claude Code, Codex |
| Artdanielmiessler/LifeOS | Skill | 20k | yesterday | MIT | A | 157 | Claude Code, Codex |
| RichFormatdanielmiessler/LifeOS | Skill | 20k | yesterday | MIT | A | 164 | Claude Code, Codex |
| Excalidrawdanielmiessler/LifeOS | Skill | 20k | yesterday | MIT | A | 131 | Claude Code, Codex |
| ApertureOscillationdanielmiessler/LifeOS | Skill | 20k | yesterday | MIT | A | 102 | Claude Code, Codex |
| learntw93/Waza | Skill | 7.5k | 4d ago | MIT | A | 39 | Claude Code |