Stop writing DTOs three times. One TypeScript type drives a NestJS endpoint,
a typed client SDK, an OpenAPI document, and e2e tests — for free.
No `class-validator`. No `@ApiProperty`. No codegen round-trip.
@TypedBody() input: IArticleCreate
SDK Generation Magic
Write NestJS controllers as you normally would. Nestia analyzes your TypeScript types and generates a fully type-safe SDK — like tRPC, but fully automated.
Your NestJS Controller
import { TypedBody, TypedParam, TypedRoute } from "@nestia/core";
import { Controller } from "@nestjs/common";
import { IBbsArticle } from "@api/lib/structures/IBbsArticle";
@Controller("bbs/:section/articles")
export class BbsArticlesController {
@TypedRoute.Post()
async create(
@TypedParam("section") section: string,
@TypedBody() input: IBbsArticle.ICreate,
): Promise<IBbsArticle> {
// no extra schema, no decorator tricks
// just pure TypeScript type
return this.service.create(section, input);
}
}Auto-generated SDK
import api from "@my/api";
import { IBbsArticle } from "@my/api/lib/structures/IBbsArticle";
// auto-generated SDK — fully type-safe
const connection: api.IConnection = {
host: "http://localhost:3000",
};
const article: IBbsArticle =
await api.functional.bbs.articles.create(
connection,
"general",
{
title: "Hello World",
body: "My first article",
thumbnail: "https://example.com/img.png",
} satisfies IBbsArticle.ICreate,
);Key Features
One library. Pure TypeScript types. Everything you need for NestJS.
Why Nestia?
Traditional NestJS development requires separate schemas, manual SDK writing, and verbose decorators. Nestia eliminates all of that with pure TypeScript types.
Traditional NestJS
✕
Define class-validator decorators on every DTO property — verbose and error-prone
✕
Write Swagger decorators manually (@ApiProperty, @ApiResponse) for documentation
✕
Generate SDK with Swagger codegen — untyped, unreliable, and hard to maintain
✕
No mockup simulator — frontend team must wait for backend implementation
✕
Manual integration needed for AI/LLM function calling with your API
Nestia — Pure TypeScript
✓
Write pure TypeScript interfaces — no decorators, no duplication, 20,000x faster validation
✓
Swagger document auto-generated from TypeScript types — always in sync with code
✓
Type-safe SDK auto-generated — like tRPC but requires zero code modification
✓
Built-in mockup simulator in SDK — frontend can start development immediately
✓
One-command AI chatbot — convert Swagger to LLM function calling schemas instantly
Mockup Simulator
SDK-embedded simulator that mimics your backend API.
Just set simulate: true — no server required.
Frontend without Backend
import api from "@my/api";
import { IBbsArticle } from "@my/api/lib/structures/IBbsArticle";
// just set simulate: true — no backend needed
const connection: api.IConnection = {
host: "http://localhost:3000",
simulate: true,
};
// same SDK function, but runs locally
// validates input with typia.assert<T>()
// returns random data with typia.random<T>()
const article: IBbsArticle =
await api.functional.bbs.articles.create(
connection,
"general",
{
title: "Hello World",
body: "My first article",
thumbnail: "https://example.com/img.png",
} satisfies IBbsArticle.ICreate,
);✅
Input Validation
Every request parameter is validated with typia.assert<T>(). Type errors are caught instantly, even without a running server.
🎲
Random Response
Generates realistic mock responses with typia.random<T>(). Respects type constraints, formats, and custom tags.
⚡
Frontend First
Start frontend development immediately. No need to wait for backend implementation — the simulator covers the full API surface.
🔄
Seamless Switch
Just remove simulate: true to connect to the real backend. Same code, same types, zero migration effort.
Sponsors
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