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 skills/fellipeutaka/leon/nestjsnpx skills add fellipeutaka/leon --skill nestjsgit clone --depth 1 https://github.com/fellipeutaka/leonWrote 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/fellipeutaka/leon/nestjs)<a href="https://agentmods.dev/skills/fellipeutaka/leon/nestjs"><img src="https://agentmods.dev/badge/skills/fellipeutaka/leon/nestjs.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 | $0.00217 | $0.02368 |
| Opus 5 | $0.00109 | $0.01184 |
| Sonnet 5 | $0.00043 | $0.00474 |
| Haiku 4.5 | $0.00022 | $0.00237 |
Grade A, and why
nestjs 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 5d 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 — 309 lines — stays where its author put it; the contents beside it link to each section on GitHub.
NestJS
Version: @nestjs/core@latest | Node >= 20 | TypeScript required
Quick Setup
npm i -g @nestjs/cli
nest new my-app
Production-ready main.ts:
import { NestFactory, Reflector } from '@nestjs/core';
import { ClassSerializerInterceptor, ValidationPipe, VersioningType } from '@nestjs/common';
import { AppModule } from './app.module';
async function bootstrap() {
const app = await NestFactory.create(AppModule);
app.useGlobalPipes(new ValidationPipe({
whitelist: true,
forbidNonWhitelisted: true,
transform: true,
transformOptions: { enableImplicitConversion: true },
}));
app.useGlobalInterceptors(new ClassSerializerInterceptor(app.get(Reflector)));
app.enableVersioning({ type: VersioningType.URI });
app.enableShutdownHooks();
await app.listen(process.env.PORT ?? 3000);
}
bootstrap();
Application Structure
Organize by feature, not by technical layer:
src/
├── users/
│ ├── dto/
│ │ ├── create-user.dto.ts
│ │ └── update-user.dto.ts
│ ├── entities/user.entity.ts
│ ├── users.controller.ts
│ ├── users.service.ts
│ └── users.module.ts
├── shared/
│ ├── guards/
│ ├── interceptors/
│ ├── filters/
│ └── shared.module.ts
└── app.module.ts
@Module() property |
Purpose |
|---|---|
providers |
Services, repositories — instantiated by DI container |
controllers |
Route handlers |
imports |
Other modules whose exports are needed here |
exports |
Subset of providers made available to importing modules |
Building Blocks
| Concept | Decorator | Purpose |
|---|---|---|
| Controller | @Controller() |
Route handlers, HTTP methods |
| Provider/Service | @Injectable() |
Business logic, DI token |
| Module | @Module() |
Feature encapsulation |
| Guard | @UseGuards() |
Auth/authz — returns boolean |
| Interceptor | @UseInterceptors() |
Transform req/res, logging, caching |
| Pipe | @UsePipes() |
Validate/transform input |
| Exception Filter | @UseFilters() |
Centralized error handling |
| Middleware | configure(consumer) |
Cross-cutting before guards |
| Decorator | createParamDecorator() |
Param extraction, metadata |
What ships with it
12 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.
- agents/openai.yaml 186 B
- rules/advanced.md 9.0 KB
- rules/arch-di.md 5.4 KB
- rules/arch-modules.md 5.9 KB
- rules/config-lifecycle.md 6.4 KB
- rules/database.md 6.6 KB
- rules/error-handling.md 6.4 KB
- rules/graphql.md 8.1 KB
- rules/http-layer.md 9.6 KB
- rules/performance.md 5.8 KB
- rules/security.md 8.6 KB
- rules/testing.md 6.3 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.
- 5d ago First seen · 309 lines · 217 tokens per session scan A 6d32bdbd0129
nestjs is a skill published in the GitHub repository fellipeutaka/leon (5 stars, last pushed yesterday), licensed MIT. It adds 217 tokens to every session and 2,368 once invoked, about $0.0011 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 2026-08-31.
Other skills, from other repositories
lint-js
Lint JS/TS code only. Use before opening a PR when only JavaScript or TypeScript files were changed (no Rust).
no-bare-casts
Writing as in TypeScript or TSX production code, modifying a file that contains a bare as cast, silencing a type error with a cast, encountering as unknown as, or reviewing a cast site.
dd-code-generation
Use pup CLI for immediate Datadog operations or generate code for integration into applications.
migrate-better-result-3
Migrate a TypeScript codebase from better-result 2.x to 3.0. Use when upgrading better-result across the TaggedError syntax, removed Result serialization helpers, recovery inference, matching, or retry APIs.
fast-typescript-check
Keep www-sacred's TypeScript fast to type-check and fast to run. Use when touching the ASCII/canvas animation components (the only real per-frame code here), tightening type-check wall-clock, or auditing a change for runtime or compiler regressions. Scoped to this repo — a React 19 / Next.js 16 component library plus…
typescript-magician
Designs complex generic types, refactors any types to strict alternatives, creates type guards and utility types, and resolves TypeScript compiler errors. Use when the user asks about TypeScript (TS) types, generics, type inference, type guards, removing any types, strict typing, type errors, infer, extends…