MCP Custom Tools

This is a Model Context Protocol (MCP) server built with Zuplo that demonstrates how to create custom MCP tools that orchestrate multiple API calls using an OpenAPI-defined API.

About this example

This project implements a Travel Advisor with MCP integration that showcases:

MCP Custom Tool

• plan-trip - A custom tool that aggregates weather forecasts, activity recommendations, and packing suggestions into a comprehensive travel brief for any destination

Key Features

This example demonstrates how to build an MCP tool that:

• Orchestrates multiple API calls - The plan-trip tool internally calls three separate endpoints (/weather, /activities, /packing)
• Processes and combines data - Analyzes weather patterns to filter activities and adjust packing recommendations
• Returns structured responses - Provides a single, comprehensive JSON response optimized for LLM consumption

Key Components

• OpenAPI-based Routes (config/routes.oas.json) - API routes with MCP annotations
• Custom Tool Handler (modules/plan-trip.ts) - Orchestration logic that combines multiple data sources

Prerequisites

• A Zuplo account. You can sign up for free.

Getting Started

Locally

Working locally is the best way to explore and understand the code for this example. You can get a local version by using the Zuplo CLI:

npx create-zuplo-api@latest --example mcp-server-custom-tools

Environment Setup

Copy the example environment file and configure the BASE_URL:

cp env.example .env

For the BASE_URL, you can use the provided Mockbin API:

BASE_URL=https://deb522471fb24e4b842dc20ea3a01c75_oas.api.mockbin.io

Alternatively, upload the travel-plan-api-oas.json file to Mockbin or another mock API service to create your own endpoints.

Note: When deploying to Zuplo, set environment variables in the Settings > Environment Variables section of your project in the Zuplo Portal.

Once you have the code on your local machine and environment configured, start the development server:

npm run dev

The API will be available at http://localhost:9000.

You can access:

• API Gateway - http://localhost:9000
• Local API Route Designer - http://localhost:9100
• MCP Endpoint - http://localhost:9000/mcp (POST)

The dev server will automatically reload when you modify:

• Route definitions in config/routes.oas.json
• Handler modules in modules/

Deploying with Zuplo CLI

Install the Zuplo CLI

npm install -g zuplo

Login to Zuplo

zuplo login

Create a New Project

zuplo init

Follow the prompts to create a new project in your Zuplo account.

Deploy to Zuplo

Deploy to a working copy environment:

zuplo deploy

Using the MCP Server

Once deployed, you can connect to your MCP server using any MCP testing tool:

Model Context Protocol Inspector

npx @modelcontextprotocol/inspector

MCPJam

npx @mcpjam/inspector@latest

You can then test the MCP server locally, or point your inspector at a deployed version.

Local MCP Server

http://localhost:9000/mcp

Deployed MCP Server

https://your-project.zuplo.app/mcp

The server will expose 1 custom tool, plan-trip, that demonstrates API orchestration for travel planning.

Example Usage

Try asking the MCP tool:

• "I'm planning a trip to Tokyo, what should I know?"
• "Help me plan a trip to Tokyo"
• "What should I pack for Tokyo"

The tool will automatically fetch weather data, recommend activities, and suggest packing items based on the destination's climate.

Learn More

• Zuplo MCP Documentation