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.
git clone --depth 1 https://github.com/fumito-ito/mdcvalultWrote 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/rules/fumito-ito/mdcvalult/best-practices-for-writitng-nextjs)<a href="https://agentmods.dev/rules/fumito-ito/mdcvalult/best-practices-for-writitng-nextjs"><img src="https://agentmods.dev/badge/rules/fumito-ito/mdcvalult/best-practices-for-writitng-nextjs/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/rules/fumito-ito/mdcvalult/best-practices-for-writitng-nextjs"><img src="https://agentmods.dev/badge/rules/fumito-ito/mdcvalult/best-practices-for-writitng-nextjs.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 | $0.00000 | $0.00588 |
| Opus 5 | $0.00000 | $0.00294 |
| Sonnet 5 | $0.00000 | $0.00118 |
| Haiku 4.5 | $0.00000 | $0.00059 |
Grade A, and why
best-practices-for-writitng-nextjs 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 10d 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 — 144 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Next.js 14 Standards
Core Features
App Router
routing_patterns:
- Use app directory for new routes
- Implement parallel routes where needed
- Leverage intercepting routes
- Use loading.tsx for suspense
- Implement error.tsx boundaries
conventions:
layout:
- Root layout with required html/body tags
- Shared UI in layout components
- Template components for variations
components:
- Server components by default
- 'use client' for client components
- Interleaved client/server architecture
Data Fetching
patterns:
server_components:
- Async components
- Direct database queries
- API integrations
- Server-side fetch
caching:
- Route cache
- Router cache
- Full route cache
- Data cache
mutations:
- Server actions
- Form actions
- Optimistic updates
- Revalidation
Rendering Patterns
strategies:
static:
- Default rendering mode
- Build-time generation
- Revalidation options
dynamic:
- Dynamic functions
- Cookies/headers
- Search params
- Dynamic segments
streaming:
- Loading states
- Suspense boundaries
- Streaming SSR
Best Practices
Performance
optimizations:
images:
- Use next/image
- Proper sizing
- Loading strategies
- Format optimization
javascript:
- Route grouping
- Component chunking
- Dynamic imports
- Bundle analysis
styles:
- CSS modules
- Tailwind integration
- CSS-in-JS solutions
- Critical CSS
Security
guidelines:
headers:
- CSP configuration
- CORS policies
- Security headers
auth:
- Auth.js integration
- Middleware usage
- Route protection
data:
- Input validation
- SQL injection prevention
- XSS protection
Development
practices:
structure:
- Feature-based organization
- Shared components
- Utils separation
- Type definitions
testing:
- Jest configuration
- React Testing Library
- E2E with Playwright
- API testing
tooling:
- ESLint setup
- Prettier config
- TypeScript strict mode
- Husky hooks
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.
- 10d ago First seen · 144 lines · 0 tokens per session scan A 42b9b999a566
best-practices-for-writitng-nextjs is a cursor rule published in the GitHub repository fumito-ito/mdcvalult (33 stars, last pushed 1y ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 588 tokens. 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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