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feat(mcp): add MCP extension for exposing APIs as MCP tools #11564
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| Original file line number | Diff line number | Diff line change |
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| --- | ||
| lang: en | ||
| title: 'Model Context Protocol (MCP)' | ||
| keywords: LoopBack 4.0, LoopBack 4, Node.js, TypeScript, OpenAPI, MCP | ||
| layout: readme | ||
| source: loopback-next | ||
| file: extensions/mcp/README.md | ||
| sidebar: lb4_sidebar | ||
| permalink: /doc/en/lb4/MCP.html | ||
| summary: Use `@loopback/mcp` to expose LoopBack APIs as MCP tools | ||
| --- |
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| @@ -0,0 +1,2 @@ | ||
| package-lock=true | ||
| scripts-prepend-node-path=true |
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| Copyright (c) LoopBack contributors 2026. | ||
| Node module: @loopback/mcp | ||
| This project is licensed under the MIT License, full text below. | ||
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| --- | ||
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| MIT license | ||
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| Permission is hereby granted, free of charge, to any person obtaining a copy | ||
| of this software and associated documentation files (the "Software"), to deal | ||
| in the Software without restriction, including without limitation the rights | ||
| to use, copy, modify, merge, publish, distribute, sublicense, and/or sell | ||
| copies of the Software, and to permit persons to whom the Software is | ||
| furnished to do so, subject to the following conditions: | ||
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| The above copyright notice and this permission notice shall be included in | ||
| all copies or substantial portions of the Software. | ||
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| THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR | ||
| IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, | ||
| FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE | ||
| AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER | ||
| LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, | ||
| OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN | ||
| THE SOFTWARE. |
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,135 @@ | ||
| <a href="https://sourcefuse.github.io/arc-docs/arc-api-docs" target="_blank"><img src="https://github.com/sourcefuse/loopback4-microservice-catalog/blob/master/docs/assets/logo-dark-bg.png?raw=true" alt="ARC By SourceFuse logo" title="ARC By SourceFuse" align="right" width="150" /></a> | ||
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| # [loopback4-mcp](https://github.com/sourcefuse/loopback4-mcp) | ||
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| <p align="left"> | ||
| <a href="https://www.npmjs.com/package/loopback4-mcp"> | ||
| <img src="https://img.shields.io/npm/v/loopback4-mcp.svg" alt="npm version" /> | ||
| </a> | ||
| <a href="https://sonarcloud.io/summary/new_code?id=sourcefuse_loopback4-mcp" target="_blank"> | ||
| <img alt="Sonar Quality Gate" src="https://img.shields.io/sonar/quality_gate/sourcefuse_loopback4-mcp?server=https%3A%2F%2Fsonarcloud.io"> | ||
| </a> | ||
| <a href="https://github.com/sourcefuse/loopback4-mcp/graphs/contributors" target="_blank"> | ||
| <img alt="GitHub contributors" src="https://img.shields.io/github/contributors/sourcefuse/loopback4-mcp?"> | ||
| </a> | ||
| <a href="https://www.npmjs.com/package/loopback4-mcp" target="_blank"> | ||
| <img alt="downloads" src="https://img.shields.io/npm/dw/loopback4-mcp.svg"> | ||
| </a> | ||
| <a href="./LICENSE"> | ||
| <img src="https://img.shields.io/github/license/sourcefuse/loopback4-mcp.svg" alt="License" /> | ||
| </a> | ||
| <a href="https://loopback.io/" target="_blank"> | ||
| <img alt="Powered By LoopBack 4" src="https://img.shields.io/badge/Powered%20by-LoopBack 4-brightgreen" /> | ||
| </a> | ||
| </p> | ||
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| ## Overview | ||
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| This extension provides a plug-and-play integration between LoopBack4 applications and the Model Context Protocol (MCP) specification. | ||
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| Its purpose is to enable LoopBack APIs, services, and business logic to be exposed as MCP Tools, allowing external MCP clients (such as LLMs, agents, or MCP-compatible apps) to discover and execute server-defined operations. | ||
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| ### Key Features | ||
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| - Automatic MCP Tool Discovery :- | ||
| The extension scans your application at boot time and automatically registers all methods decorated with the custom @mcpTool() decorator. | ||
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| This allows you to define MCP tools anywhere in your LoopBack project without manually wiring metadata. | ||
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| - Lifecycle-managed Tool Registry :- | ||
| A dedicated `McpToolRegistry` service maintains all discovered tool metadata,their handlers and execution context. | ||
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| A `McpToolRegistryBootObserver` ensures that registration happens only after the application has fully booted. | ||
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| ## Installation | ||
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| ```sh | ||
| npm install @loopback/mcp | ||
| ``` | ||
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| ## Basic Usage | ||
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| Configure and load `McpComponent` in the application constructor | ||
| as shown below. | ||
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| ```ts | ||
| import {McpComponent} from 'loopback4-mcp'; | ||
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| export class MyApplication extends BootMixin( | ||
| ServiceMixin(RepositoryMixin(RestApplication)), | ||
| ) { | ||
| constructor(options: ApplicationConfig = {}) { | ||
| super(); | ||
| this.component(McpComponent); | ||
| } | ||
| } | ||
| ``` | ||
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| Add the `@mcpTool()` decorator to any controller in your application. | ||
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| All MCP tool methods must use LoopBack `@param` decorators to define their input parameters.If `@param` decorators are missing, the MCP tool will fail. | ||
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| ```ts | ||
| @mcpTool({ | ||
| name: 'create-user', | ||
| description: 'Creates a new user in the system', | ||
| schema?: { | ||
| email: z.string().email(), | ||
| name: z.string(), | ||
| }, | ||
| }) | ||
| async createUser( | ||
| @param.query.string('email') email: string, | ||
| @param.query.string('name') name: string, | ||
| ) { | ||
| return {message: `User ${name} created`}; | ||
| } | ||
| ``` | ||
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| This decorator accepts a total of five fields, out of which `name` and `description` are mandatory and `schema`,`preHook` and `postHook` are optional enhancements. | ||
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| The schema field allows defining a Zod-based validation schema for tool input parameters, while preHook and postHook enable execution of custom logic before and after the tool handler runs. | ||
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| ## Mcp Hook Usage Details | ||
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| To use hooks with MCP tools, follow the provider-based approach: | ||
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| Step 1: Create a hook provider: | ||
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| ```ts | ||
| // src/providers/my-hook.provider.ts | ||
| export class MyHookProvider implements Provider<McpHookFunction> { | ||
| constructor(@inject(LOGGER.LOGGER_INJECT) private logger: ILogger) {} | ||
| value(): McpHookFunction { | ||
| return async (context: McpHookContext) => { | ||
| this.logger.info(`Hook executed for tool: ${context.toolName}`); | ||
| }; | ||
| } | ||
| } | ||
| ``` | ||
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| Step 2: Add binding key to McpHookBindings: | ||
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| ```ts | ||
| // src/keys.ts | ||
| export namespace McpHookBindings { | ||
| export const MY_HOOK = BindingKey.create<McpHookFunction>('hooks.mcp.myHook'); | ||
| } | ||
| ``` | ||
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| Step 3: Bind provider in `application.ts`: | ||
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| ```typescript | ||
| this.bind(McpHookBindings.MY_HOOK).toProvider(MyHookProvider); | ||
| ``` | ||
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| Step 4: Use in decorator: | ||
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| ```ts | ||
| @mcpTool({ | ||
| name: 'my-tool', | ||
| description: 'my-description' | ||
| preHookBinding: McpHookBindings.MY_HOOK, | ||
| postHookBinding: 'hooks.mcp.myOtherHook' // or string binding key | ||
| }) | ||
| ``` | ||
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| { | ||
| "name": "@loopback/mcp", | ||
| "version": "0.0.1", | ||
| "private": false, | ||
| "description": "A loopback extension that exposes API to MCP Tools.", | ||
| "keywords": [ | ||
| "loopback-extension", | ||
| "loopback", | ||
| "loopback4", | ||
| "mcp", | ||
| "mcp-tool" | ||
| ], | ||
| "main": "dist/index.js", | ||
| "types": "dist/index.d.ts", | ||
| "engines": { | ||
| "node": ">=20" | ||
| }, | ||
| "scripts": { | ||
| "build": "lb-tsc", | ||
| "build:watch": "lb-tsc --watch", | ||
| "lint": "npm run eslint && npm run prettier:check", | ||
| "lint:fix": "npm run eslint:fix && npm run prettier:fix", | ||
| "prettier:cli": "lb-prettier \"**/*.ts\" \"**/*.js\"", | ||
| "prettier:check": "npm run prettier:cli -- -l", | ||
| "prettier:fix": "npm run prettier:cli -- --write", | ||
| "eslint": "lb-eslint --report-unused-disable-directives .", | ||
| "eslint:fix": "npm run eslint -- --fix", | ||
| "pretest": "npm run rebuild", | ||
| "test": "lb-mocha --allow-console-logs \"dist/__tests__\"", | ||
| "posttest": "npm run lint", | ||
| "test:dev": "lb-mocha --allow-console-logs dist/__tests__/**/*.js && npm run posttest", | ||
| "clean": "lb-clean dist *.tsbuildinfo .eslintcache", | ||
| "rebuild": "npm run clean && npm run build", | ||
| "prepublishOnly": "npm run test" | ||
| }, | ||
| "repository": { | ||
| "type": "git", | ||
| "url": "https://github.com/sourcefuse/loopback4-mcp" | ||
| }, | ||
| "author": "SourceFuse", | ||
| "license": "MIT", | ||
| "files": [ | ||
| "README.md", | ||
| "dist", | ||
| "src", | ||
| "!*/__tests__" | ||
| ], | ||
| "peerDependencies": { | ||
| "@loopback/core": "^7.0.3" | ||
| }, | ||
| "dependencies": { | ||
| "@loopback/rest": "^15.0.7", | ||
| "@modelcontextprotocol/sdk": "^1.24.0", | ||
| "@sourceloop/core": "^20.0.0", | ||
| "tslib": "^2.6.2", | ||
| "zod": "^4.2.1" | ||
| }, | ||
| "devDependencies": { | ||
| "@commitlint/cli": "^17.7.1", | ||
| "@commitlint/config-conventional": "^17.7.0", | ||
| "@loopback/boot": "^8.0.11", | ||
| "@loopback/build": "^12.0.3", | ||
| "@loopback/core": "^7.0.3", | ||
| "@loopback/eslint-config": "^16.0.1", | ||
| "@loopback/repository": "^8.0.10", | ||
| "@loopback/rest-explorer": "^8.0.11", | ||
| "@loopback/service-proxy": "^8.0.10", | ||
| "@loopback/testlab": "^8.0.3", | ||
| "@semantic-release/changelog": "^6.0.1", | ||
| "@semantic-release/commit-analyzer": "^9.0.2", | ||
| "@semantic-release/git": "^10.0.1", | ||
| "@semantic-release/npm": "^13.1.3", | ||
| "@semantic-release/release-notes-generator": "^10.0.3", | ||
| "@types/jsonwebtoken": "^9.0.10", | ||
| "@types/node": "^16.18.126", | ||
| "commitizen": "^4.2.4", | ||
| "cz-conventional-changelog": "^3.3.0", | ||
| "cz-customizable": "^6.3.0", | ||
| "cz-customizable-ghooks": "^2.0.0", | ||
| "eslint": "^8.57.1", | ||
| "husky": "^7.0.4", | ||
| "loopback4-authentication": "^13.0.4", | ||
| "loopback4-authorization": "^8.1.3", | ||
| "semantic-release": "^25.0.2", | ||
| "source-map-support": "^0.5.21", | ||
| "typescript": "~5.2.2" | ||
| }, | ||
| "overrides": { | ||
| "jws": "3.2.3", | ||
| "node-forge": "1.3.2", | ||
| "qs": "6.14.1" | ||
| }, | ||
| "config": { | ||
| "commitizen": { | ||
| "path": "./node_modules/cz-customizable" | ||
| }, | ||
| "cz-customizable": { | ||
| "config": "./.cz-config.js" | ||
| } | ||
| }, | ||
| "publishConfig": { | ||
| "registry": "https://registry.npmjs.org/", | ||
| "access": "public" | ||
| }, | ||
| "release": { | ||
| "branches": [ | ||
| "master" | ||
| ], | ||
| "plugins": [ | ||
| [ | ||
| "@semantic-release/commit-analyzer", | ||
| { | ||
| "preset": "angular", | ||
| "releaseRules": [ | ||
| { | ||
| "type": "chore", | ||
| "scope": "deps", | ||
| "release": "patch" | ||
| } | ||
| ] | ||
| } | ||
| ], | ||
| "@semantic-release/release-notes-generator", | ||
| [ | ||
| "@semantic-release/npm", | ||
| { | ||
| "npmPublish": true, | ||
| "pkgRoot": ".", | ||
| "tarballDir": "dist" | ||
| } | ||
| ], | ||
| [ | ||
| "@semantic-release/git", | ||
| { | ||
| "assets": [ | ||
| "package.json", | ||
| "CHANGELOG.md" | ||
| ], | ||
| "message": "chore(release): ${nextRelease.version} semantic" | ||
| } | ||
| ], | ||
| "@semantic-release/github" | ||
| ], | ||
| "repositoryUrl": "https://github.com/sourcefuse/loopback4-mcp.git" | ||
| } | ||
| } |
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change the naming here