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 nweii/agent-stuff --skill react-useeffectgit clone --depth 1 https://github.com/nweii/agent-stuffWrote 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/nweii/agent-stuff/react-useeffect)<a href="https://agentmods.dev/skills/nweii/agent-stuff/react-useeffect"><img src="https://agentmods.dev/badge/skills/nweii/agent-stuff/react-useeffect/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/nweii/agent-stuff/react-useeffect"><img src="https://agentmods.dev/badge/skills/nweii/agent-stuff/react-useeffect.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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 | $0.00039 | $0.00567 |
| Opus 5.5 | $0.00016 | $0.00227 |
| Sonnet 5.5 | $0.00008 | $0.00113 |
| Haiku 4.5 | $0.00004 | $0.00057 |
Grade A, and why
react-useeffect 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.
This is a copy
84% identical to react-useeffect — 5 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 57 lines — stays where its author put it; the contents beside it link to each section on GitHub.
You Might Not Need an Effect
Effects are an escape hatch from React. They let you synchronize with external systems. If there is no external system involved, you shouldn't need an Effect.
Quick Reference
| Situation | DON'T | DO |
|---|---|---|
| Derived state from props/state | useState + useEffect |
Calculate during render |
| Expensive calculations | useEffect to cache |
useMemo |
| Reset state on prop change | useEffect with setState |
key prop |
| User event responses | useEffect watching state |
Event handler directly |
| Notify parent of changes | useEffect calling onChange |
Call in event handler |
| Fetch data | useEffect without cleanup |
useEffect with cleanup OR framework |
When You DO Need Effects
- Synchronizing with external systems (non-React widgets, browser APIs)
- Subscriptions to external stores (use
useSyncExternalStorewhen possible) - Analytics/logging that runs because component displayed
- Data fetching with proper cleanup (or use framework's built-in mechanism)
When You DON'T Need Effects
- Transforming data for rendering - Calculate at top level, re-runs automatically
- Handling user events - Use event handlers, you know exactly what happened
- Deriving state - Just compute it:
const fullName = firstName + ' ' + lastName - Chaining state updates - Calculate all next state in the event handler
Decision Tree
Need to respond to something?
├── User interaction (click, submit, drag)?
│ └── Use EVENT HANDLER
├── Component appeared on screen?
│ └── Use EFFECT (external sync, analytics)
├── Props/state changed and need derived value?
│ └── CALCULATE DURING RENDER
│ └── Expensive? Use useMemo
└── Need to reset state when prop changes?
└── Use KEY PROP on component
Detailed Guidance
- Anti-Patterns - Common mistakes with fixes
- Better Alternatives - useMemo, key prop, lifting state, useSyncExternalStore
What ships with it
2 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.
- 1mo ago First seen · 57 lines · 39 tokens per session scan A b41091b7bcdc
react-useeffect is a skill published in the GitHub repository nweii/agent-stuff (10 stars, last pushed 3d ago), licensed MIT. It adds 39 tokens to every session and 567 once invoked, about $0.0002 per session on Opus 5.5. A static security scan graded it A with 0 findings. It is 84% identical to react-useeffect, differing in 5 lines, and is treated as a copy.
Other skills, from other repositories
chakra-ui-builder
Build responsive, accessible UI components and layouts using Chakra UI v3, install or configure Chakra UI in new and existing projects, and design scalable themes using tokens, semantic tokens, recipes, and slot recipes. Use this skill whenever a user asks to build, create, or generate any UI component, page, form…
material-ui-tailwind
Integrates Material UI with Tailwind CSS v4 using cascade layers (enableCssLayer, @layer order) and documents Tailwind v3 interoperability (preflight, important, injectFirst, portals). Use when combining MUI with Tailwind utilities, slotProps className, or theme token bridges.
fuzzy-ranking
Rank fuzzy matches with rankItem, filter with RankingInfo.passed, compare saved ranking metadata with compareItems, and configure rankings, thresholds, accessors, min/max bounds, or diacritics. Load for @tanstack/match-sorter-utils itself or fuzzy Table filterMeta wiring.
r3f-best-practices
React Three Fiber (R3F) and Poimandres ecosystem best practices. Use when writing, reviewing, or optimizing R3F code. Triggers on tasks involving @react-three/fiber, @react-three/drei, zustand, @react-three/postprocessing, @react-three/rapier, or leva.
git-safety
Git safety rules. INVOKE WHEN: git push, force push, git reset, git clean, destructive git, push force, reset hard. NEVER force push or do destructive git operations.
onchainkit
Build onchain apps with Coinbase's OnchainKit React components - wallets, swaps, NFTs, payments.