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 react-best-practicesgit 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/react-best-practices)<a href="https://agentmods.dev/skills/majiayu000/spellbook/react-best-practices"><img src="https://agentmods.dev/badge/skills/majiayu000/spellbook/react-best-practices/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/react-best-practices"><img src="https://agentmods.dev/badge/skills/majiayu000/spellbook/react-best-practices.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 | $0.00050 | $0.00884 |
| Opus 5.5 | $0.00020 | $0.00354 |
| Sonnet 5.5 | $0.00010 | $0.00177 |
| Haiku 4.5 | $0.00005 | $0.00088 |
Grade A, and why
react-best-practices 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 1mo 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 — 106 lines — stays where its author put it; the contents beside it link to each section on GitHub.
React Best Practices
Practical React and Next.js guidance for performance-sensitive product work.
This skill is a self-contained distillation of the Vercel React performance guidance so it can be installed and used directly inside Spellbook.
When To Use
Use this skill when the user asks to:
- build or refactor React components
- improve Next.js performance
- reduce bundle size
- remove data-fetch waterfalls
- fix expensive rerenders
- review frontend code for performance issues
Priority Order
Always check higher-priority categories first.
| Priority | Category | Focus |
|---|---|---|
| 1 | Waterfalls | start async work early, await late, parallelize independent fetches |
| 2 | Bundle size | avoid barrel imports, defer heavy code, split by feature |
| 3 | Server-side performance | dedupe work, minimize serialization, prefer server execution |
| 4 | Client data fetching | dedupe requests, avoid redundant listeners and client churn |
| 5 | Rerenders | reduce subscriptions, stabilize dependencies, move expensive work |
| 6 | Rendering | avoid hydration flicker, reduce DOM/SVG cost, optimize long lists |
| 7 | JavaScript hot paths | cache repeated lookups, combine iterations, exit early |
| 8 | Advanced patterns | stable refs and callback patterns for edge cases |
Hard Rules
1. Eliminate Waterfalls First
- Start independent requests in parallel.
- Do not serialize async work unless there is a real dependency.
- In API routes and server components, create promises early and await them as late as possible.
- Use Suspense boundaries when streaming content helps unblock rendering.
2. Protect Bundle Size
- Prefer direct imports over barrel files on hot paths.
- Use dynamic imports for heavy or infrequently used components.
- Defer analytics, logging, and other non-critical third-party code until after hydration.
- Load optional modules only when the related feature is activated.
3. Prefer Server Work Over Client Work
- Keep data fetching and heavy transformation on the server when possible.
- Minimize data serialized into client components.
- Cache server-side repeated work when the request model allows it.
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.
- 1mo ago First seen · 106 lines · 50 tokens per session scan A 5d221600c5af
react-best-practices is a skill published in the GitHub repository majiayu000/spellbook (288 stars, last pushed yesterday), licensed MIT. It adds 50 tokens to every session and 884 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.
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