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 magnus919/agent-skills --skill frontend-engineeringgit clone --depth 1 https://github.com/magnus919/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/magnus919/agent-skills/frontend-engineering)<a href="https://agentmods.dev/skills/magnus919/agent-skills/frontend-engineering"><img src="https://agentmods.dev/badge/skills/magnus919/agent-skills/frontend-engineering/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/magnus919/agent-skills/frontend-engineering"><img src="https://agentmods.dev/badge/skills/magnus919/agent-skills/frontend-engineering.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 | $0.00058 | $0.01166 |
| Opus 5.5 | $0.00023 | $0.00466 |
| Sonnet 5.5 | $0.00012 | $0.00233 |
| Haiku 4.5 | $0.00006 | $0.00117 |
Grade A, and why
frontend-engineering 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
89% identical to frontend-engineering — 41 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 — 69 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Frontend Engineering Methodology
Frontend engineering is the craft of building the user-facing layer of applications — components, state management, API integration, responsive layout, and client-side performance. This methodology bridges UX design (user journeys, wireframes, accessibility standards) and quality validation (qa-methodology).
The Frontend Engineer's Domain
| You own | You don't own |
|---|---|
| Component implementation — UI component composition, props/state interfaces, rendering patterns, lifecycle | User journeys, wireframes, accessibility standards, interaction design — that's the product-design-and-ux |
| State management — client-side state architecture, data fetching patterns, caching, optimistic updates | API contract design — that's the api-design-and-evolution |
| API integration — frontend-to-backend data flow, auth flows (OAuth, JWT), real-time updates | Test strategy and automation — that's the QA-engineer |
| Responsive design implementation — layout systems, breakpoints, cross-device testing | Visual identity and brand guidelines — that's the brand-designer |
| Client-side performance — bundle optimization, lazy loading, Core Web Vitals, render optimization | Editorial content and copy — owned by the content and marketing team, outside this skill's scope |
| Frontend testing — component tests, integration tests, visual regression, accessibility tests | Code review and quality gates — that's the qa-methodology |
| E2E test scenarios and user-flow coverage for frontend features | Operating the browser test tool (Playwright) — authoring/running specs, selectors, network mocking, scraping — route to playwright |
| Mobile app implementation (iOS/Android/Flutter/React Native) | Mobile platform work — scaffolding, builds and code signing, device/emulator testing, store submission, mobile lifecycle — route to mobile-development; this skill owns web frontends |
| Build tooling — bundler config, TypeScript config, linting, formatting, dev environment | CI/CD pipeline infrastructure — that's the platform-engineer |
What ships with it
11 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.
- evals/evals.json 10 KB
- README.md 2.0 KB
- references/api-integration.md 1.6 KB
- references/component-architecture.md 1.8 KB
- references/performance.md 1.4 KB
- references/responsive-layout-testing.md 32 KB
- references/state-management.md 1.8 KB
- scripts/bundle-budget-checker.py 6.3 KB runs code
- scripts/test_bundle_budget_checker.py 7.9 KB runs code
- templates/component-state-design-record.md 2.9 KB
- templates/performance-budget.md 2.8 KB
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 · +2 lines 65b7062b942d
- 1mo ago First seen · 67 lines · 58 tokens per session scan A bd5015f819f1
frontend-engineering is a skill published in the GitHub repository magnus919/agent-skills (151 stars, last pushed yesterday), licensed MIT. It adds 58 tokens to every session and 1,166 once invoked, about $0.0002 per session on Opus 5.5. A static security scan graded it A with 0 findings. It is 89% identical to frontend-engineering, differing in 41 lines, and is treated as a copy.
Other skills, from other repositories
cocoreview
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cocoharvest
Decompose an approved plan into parallel workstreams, assign specialist personas, classify stages as HITL or AFK (CocoLens), generate flow.json stages with checkpoints and dual-file state, and create per-stage prompt files. Includes adaptive parallelism, stall detection, shell identity injection, and consecutive…
spec
Enter the Spec phase of CocoBrew. Guides the developer through structured requirements capture: goal, success criteria, constraints, personas involved, data sources, and deliverables. Writes spec.md to .cocoplus/lifecycle/ and creates a git commit.
discuss
Run a structured decision-capture dialogue before $plan — locks implementation choices (model, evaluation methodology, accuracy threshold, scope boundaries) into discuss.md to prevent silent decision drift during planning. Supports --red-team flag for adversarial post-PASS challenge session.
cocotrace
Build and query the SHA-256 requirements-to-implementation traceability graph across lifecycle artifacts.
cocoscout
Relevance-ranked context loading — Tier 2 async subagent (Haiku, <5s) that fires after Tier 1 deterministic checks in UserPromptSubmit. Injects ranked context from CocoGrove, CocoContext, Environment Inspector, Prompt Studio, and CocoDream.