OpenAPI‑first utilities for NestJS
Single source of truth · Drop‑in for NestJS · Fast by design
- 🎯 Single Source of Truth — Your OpenAPI spec drives validation, serialization, mocking, and MCP tools.
- ⚡ Fast by Design — AJV validation and
fast-json-stringifyserialization with caching and precompilation. - 🔌 Drop-in Integration — Works with existing NestJS controllers and routes
- 🎛️ Fine-Grained Control — Per-route opt-out and custom schema overrides
- 🚀 Platform Agnostic — Supports both Express and Fastify adapters
| Package | Description | Version |
|---|---|---|
@nest-openapi/validator | Automatic request/response validation using your OpenAPI spec |  |
@nest-openapi/serializer | High-performance response serialization based on your OpenAPI spec |  |
@nest-openapi/mock | Spec-driven mock server for generating realistic mock responses |  |
@nest-openapi/mcp | Spec-driven MCP server for exposing OpenAPI operations as tools |  |
npm i @nest-openapi/validatorimport { Module } from "@nestjs/common"; import { OpenAPIValidatorModule } from "@nest-openapi/validator"; import * as openApiSpec from "./openapi.json"; @Module({ imports: [ OpenAPIValidatorModule.forRoot({ specSource: { type: "object", spec: openApiSpec }, }), ], }) export class AppModule {}All routes are automatically validated. See full documentation for advanced configuration.
npm i @nest-openapi/serializerimport { Module } from "@nestjs/common"; import { OpenAPISerializerModule } from "@nest-openapi/serializer"; import * as openApiSpec from "./openapi.json"; @Module({ imports: [ OpenAPISerializerModule.forRoot({ specSource: { type: "object", spec: openApiSpec }, responseSerialization: { enable: true, skipErrorResponses: true }, }), ], }) export class AppModule {}Responses are automatically serialized. See full documentation for advanced configuration.
npm i @nest-openapi/mockimport { Module } from "@nestjs/common"; import { OpenAPIMockModule } from "@nest-openapi/mock"; import * as openApiSpec from "./openapi.json"; @Module({ imports: [ OpenAPIMockModule.forRoot({ specSource: { type: "object", spec: openApiSpec }, enable: process.env.NODE_ENV === "development", mockByDefault: true, }), ], }) export class AppModule {}Routes return mocked responses when enabled. See full documentation for advanced configuration.
npm i @nest-openapi/mcpimport { Module } from "@nestjs/common"; import { OpenAPIMcpModule } from "@nest-openapi/mcp"; import * as openApiSpec from "./openapi.json"; @Module({ imports: [ OpenAPIMcpModule.forRoot({ specSource: { type: "object", spec: openApiSpec }, http: { path: "/mcp" }, executor: { baseUrl: "http://127.0.0.1:3000" }, }), ], }) export class AppModule {}Expose OpenAPI operations as MCP tools. See full documentation for advanced configuration.
import { Inject, Injectable } from "@nestjs/common"; import { OPENAPI_VALIDATOR, OpenAPIValidatorService, } from "@nest-openapi/validator"; @Injectable() export class MyService { constructor( @Inject(OPENAPI_VALIDATOR) private readonly validator: OpenAPIValidatorService, ) {} validate(ctx: HttpArgumentsHost) { const errors = this.validator.validateRequest(ctx, { body: true }); if (errors.length > 0) { // Handle validation errors } } }import { Controller, Post } from "@nestjs/common"; import { Validate } from "@nest-openapi/validator"; import { Serialize } from "@nest-openapi/serializer"; @Controller("books") export class BooksController { @Post() @Validate({ request: { query: false }, response: true }) @Serialize({ disable: true }) create(@Body() dto: CreateBookDto): Book { return this.booksService.create(dto); } }- Works with NestJS v9+
- Supports Express and Fastify adapters
Issues and PRs are welcome. Please check the package folders and docs before opening an issue.
MIT © @nest-openapi