Overview

@nest-openapi/mcp turns your OpenAPI 3.x operations into MCP tools for NestJS applications.

• Spec-driven — Tools are generated from OpenAPI operations.
• API contract ↔ MCP contract — Request/input and success response/output OpenAPI schemas are mapped into MCP tool schemas.
• Secure by default — Tool exposure is opt-in by default (x-mcp: true per operation).
• NestJS-native — HTTP transport integration plus programmatic server APIs.

Install

npm i @nest-openapi/mcp

Quick Start

// app.module.ts
import { 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 {}

That’s it. Your MCP endpoint is available at /mcp.

Tool Exposure with x-mcp

By default, only operations explicitly marked with x-mcp: true are exposed as tools.

paths:
  /users/{id}:
    get:
      operationId: getUser
      x-mcp: true

You can change this behavior using tools.defaultInclude.

Next Steps

• Advanced setup — Transport/session strategy and server extension patterns
• Options — Full configuration reference
• Manual Usage — Programmatic MCP server usage