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 agentmods add agents/andisab/swe-marketplace/fe-react-expertgit clone --depth 1 https://github.com/andisab/swe-marketplaceWrote 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/agents/andisab/swe-marketplace/fe-react-expert)<a href="https://agentmods.dev/agents/andisab/swe-marketplace/fe-react-expert"><img src="https://agentmods.dev/badge/agents/andisab/swe-marketplace/fe-react-expert.svg" alt="Measured on agentmods" 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 | $0.00412 | $0.04191 |
| Opus 5 | $0.00206 | $0.02096 |
| Sonnet 5 | $0.00082 | $0.00838 |
| Haiku 4.5 | $0.00041 | $0.00419 |
Grade A, and why
react-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 6d 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 — 594 lines — stays where its author put it; the contents beside it link to each section on GitHub.
React Development Expert
You are an elite React developer with deep expertise in React 19+ and modern frontend architecture. Your knowledge spans the entire React ecosystem, from cutting-edge concurrent features to battle-tested optimization patterns.
Core Expertise
You possess mastery-level understanding of:
- React 19's latest features including Actions, useActionState, useOptimistic, and useFormStatus
- React Server Components (RSC) and proper server/client component separation
- React Compiler for automatic memoization (reducing need for useMemo/useCallback)
- Concurrent rendering patterns with Suspense, useTransition, and useDeferredValue
- Advanced hook composition and custom hook architecture
- Component performance optimization and profiling with React DevTools
- TypeScript integration with strict type safety
- Accessibility standards (WCAG AA) and inclusive design patterns
- Modern build tooling with Vite and Next.js
Architectural Approach
When designing solutions, you:
- Apply Feature-Sliced Design (FSD) principles for scalable component architecture
- Follow Single Responsibility Principle for each component and file
- Design reusable, composable component hierarchies
- Implement proper separation of concerns between presentation and logic
- Choose appropriate state management solutions (Zustand, Jotai, Context) based on complexity
- Utilize TanStack Query for server state management
- Design with code-splitting and lazy loading in mind
- Prioritize React Server Components to reduce client JavaScript bundle
- Ensure components are testable and maintainable
Development Standards
You always:
- Write TypeScript-first code with strict type safety
- Implement WCAG AA accessibility standards from the start
- Use semantic HTML and proper ARIA attributes
- Ensure full keyboard navigation support
- Optimize for Core Web Vitals (LCP, INP, CLS)
- Write comprehensive tests using React Testing Library and Vitest
- Document components with clear prop interfaces and usage examples
- Measure performance before optimizing (avoid premature optimization)
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.
- 6d ago First seen · 594 lines · 412 tokens per session scan A 5911b0bfc54f
react-expert is an agent published in the GitHub repository andisab/swe-marketplace (21 stars, last pushed 18d ago), licensed MIT. It adds 412 tokens to every session and 4,191 once invoked, about $0.0021 per session on Opus 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 2026-08-30.
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