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 PracticalSwan/agent-skills --skill react-developmentgit clone --depth 1 https://github.com/PracticalSwan/agent-skillsWrote 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/practicalswan/agent-skills/react-development)<a href="https://agentmods.dev/skills/practicalswan/agent-skills/react-development"><img src="https://agentmods.dev/badge/skills/practicalswan/agent-skills/react-development/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/practicalswan/agent-skills/react-development"><img src="https://agentmods.dev/badge/skills/practicalswan/agent-skills/react-development.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector warn
SkillSpector: 1 finding, up to high
These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →
- high Prompt Injection · line 1161 Hidden instructions were detected in comments or invisible text. These could contain malicious directives. Manual review is recommended.Fix: Audit all comments and invisible characters. Remove any instructions that direct the agent to perform unauthorized actions. Use plain, reviewable content.
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 | $0.00049 | $0.07550 |
| Opus 5.5 | $0.00020 | $0.03020 |
| Sonnet 5.5 | $0.00010 | $0.01510 |
| Haiku 4.5 | $0.00005 | $0.00755 |
Grade A, and why
react-development scanned grade A with 1 finding 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.
Makes network callslowCapability
Not a fault in itself. Listed so you know the mod talks to something, and to what.
const response = await fetch(url); How it starts
The opening of the file, as written. The whole thing — 1,192 lines — stays where its author put it; the contents beside it link to each section on GitHub.
React Development
Optimized for React 19+, TypeScript 5.5+, React Testing Library 16+, and modern server-first app architectures.
Expert guidance for building high-quality React applications with React 19+, modern hooks, TypeScript, and best practices following official React documentation at https://react.dev.
- Leverage native parallel subagent dispatch and 200k+ context windows where available.
Component Review Rubric Reference
Apply the shared Component Review Rubric before approving React components, then run the React-specific checks below.
Cross-Client Portability
This skill is written to stay usable across GitHub Copilot, Claude Code, and Codex.
- GitHub Copilot: keep the folder in a Copilot-visible skill path or wrap the workflow in project instructions when folder discovery is unavailable.
- Claude Code: keep the folder in a local skills directory or a compatible plugin source.
- Codex: install or sync the folder into
$CODEX_HOME/skills/react-developmentand restart Codex after major changes.
MCP Availability And Fallback
Preferred MCP Server: None required
- Fallback prompt: "Use the React Development skill without MCP. Rely on its local instructions, bundled resources, standard shell or editor tools, and direct verification. Show the evidence used before concluding."
- Do not claim an MCP operation was used when the active host does not expose it.
- Treat local files, tests, rendered outputs, logs, or screenshots as the fallback evidence path.
Anti-Patterns
- Fetching everything in client effects by default: Server-first data loading is usually simpler, faster, and easier to cache.
- Adding memoization before profiling: Manual optimizations can create stale-prop bugs and hide simpler design fixes.
- Skipping keyboard and accessible-name review: A component is not done if only pointer users can operate it reliably.
What ships with it
8 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 Changed 0e5ea93f337c
- 1mo ago Changed c33262d67e3f
- 1mo ago First seen · 1,192 lines · 49 tokens per session scan A 440c5076ebc6
react-development is a skill published in the GitHub repository PracticalSwan/agent-skills (22 stars, last pushed 11d ago), licensed MIT. It adds 49 tokens to every session and 7,550 once invoked, about $0.0002 per session on Opus 5.5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.
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