Sam Serverless

A super simple Model Context Protocol (MCP) server deployed on AWS Lambda and exposed via Amazon API Gateway, deployed with Serverless Application Model (SAM). This skeleton is based on the awesome work of Frédéric Barthelet: which has developed a middy middleware for Model Context Protocol (MCP) server integration with AWS Lambda functions in this repo

Long story

📖 Read the article of this series here on dev.to

🛠 Features

• 🪄 Minimal MCP server setup using @modelcontextprotocol/sdk
• 🚀 Deployed as a single AWS Lambda function
• 🌐 HTTP POST endpoint exposed via API Gateway at /mcp
• 🔄 Supports local development via SAM
• 🧪 Includes a simple example tool (add) with JSON-RPC interaction

📦 Project Structure

sam-serverless-mcp-server/
├── __tests__/              # Jest tests
├── src/                    # Source code
│   └── index.js                # MCP server handler
├── .gitignore              # Git ignore file
├── buildspec.yml           # Buildspec file for AWS CodeBuild and CodePipeline (CI/CD)
├── jest.config.mjs         # Jest config file
├── package.json            # Project dependencies
├── package-lock.json       # Project lock file
├── README.md               # This documentation file
├── samconfig.toml          # Serverless Application Model config
└── template.yml            # Serverless Application Model template

🛠 Prerequisites

• Node.js v22+
• Docker
• AWS CLI
• SAM CLI

🚀 Getting Started

1. Install dependencies:

npm install

2. Run Locally with SAM

sam local start-api

Local endpoint will be available at: POST http://localhost:3000/mcp

Switch to Api Gateway V2 (HTTP API)

If you want to use API Gateway V2, you can change the template.yml file to use HttpApi instead of Api in the Events section. This will allow you to use HTTP APIs instead of REST APIs. This will allow you to use HTTP APIs instead of REST APIs.

Events:
  McpHttpApi:
    Type: HttpApi  # 👈 This switches to HTTP API (v2)
    Properties:
      Path: /mcp
      Method: POST

🧪 Test with curl requests

List tools

curl --location 'http://localhost:3000/mcp' \
--header 'content-type: application/json' \
--header 'accept: application/json' \
--header 'jsonrpc: 2.0' \
--data '{
  "jsonrpc": "2.0",
  "method": "tools/list",
  "id": 1
}'

➕ Use the add Tool

curl --location 'http://localhost:3000/mcp' \
--header 'content-type: application/json' \
--header 'accept: application/json' \
--header 'jsonrpc: 2.0' \
--data '{
  "jsonrpc": "2.0",
  "id": 2,
  "method": "tools/call",
  "params": {
    "name": "add",
    "arguments": {
      "a": 5,
      "b": 3
    }
  }
}'

🧪 Test with jest

There are some basic tests included in the __tests__ folder. You can run them with:

npm run test

🧬 Code Breakdown

This code is based on the awesome work of Frédéric Barthelet: which has developed a middy middleware for Model Context Protocol (MCP) server integration with AWS Lambda functions in this repo

src/index.js

import middy from "@middy/core";
import httpErrorHandler from "@middy/http-error-handler";
import { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js";
import { z } from "zod";
import mcpMiddleware from "middy-mcp";

const server = new McpServer({
  name: "Lambda hosted MCP Server",
  version: "1.0.0",
});

server.tool("add", { a: z.number(), b: z.number() }, async ({ a, b }) => ({
  content: [{ type: "text", text: String(a + b) }],
}));

export const handler = middy()
  .use(mcpMiddleware({ server }))
  .use(httpErrorHandler());

📡 Deploy to AWS

Just run:

sam build
sam deploy --guided

After deployment, the MCP server will be live at the URL output by the command.

📘 License

MIT — feel free to fork, tweak, and deploy your own version!