MCP servers

MCP is Model Context Protocol, and it's a agreed set of interfaces that shape up a kind of API that connects LLMs to traditional APIs and datasources.

It acts as a server like a language server which responds to a known set of endpoints.

In the case of MCP servers, it exposes Resources, Tools and Prompts.

Servers expose tools and resources through tools/list and resources/list endpoints. Servers call tools and read resources through tools/call and resources/read.

Usage

Getting started

To get started with TypeScript, install modelcontextprotocol/typescript-sdk:

npm install @modelcontextprotocol/sdk

Then, create a new server and wait for connections:

import { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js";
import { StdioServerTransport } from "@modelcontextprotocol/sdk/server/stdio.js";

const server = new McpServer({
  name: "Demo",
  version: "1.0.0"
});

const transport = new StdioServerTransport();
await server.connect(transport);

You'll need top-level await, see Promises.

Debugging with the Inspector

From here, you can use the MCP Inspector to check everything is working as expected.

The documentation recommends using npx instead of installing - do that if you'd prefer, but I prefer to install my tooling locally:

npm install -D @modelcontextprotocol/inspector

From here, you can start your server locally:

npx mcp-inspector node ./path/to/index.js

# If using TypeScript, it'll probably be:
npx mcp-inspector node ./dist/index.js

# If you add a shebang and add executable permissions, then you could just
npx mcp ./dist/index.js

Sample client

You can create and use a client similarly to a server:

import { Client } from "@modelcontextprotocol/sdk/client/index.js";
import { StdioClientTransport } from "@modelcontextprotocol/sdk/client/stdio.js";

const transport = new StdioClientTransport({
    command: "node",
    // For connecting to a local MCP server
    args: [join(__dirname, "..", "dist", "index.js")],
});

const client = new Client({
    name: "test-client",
    version: "0.0.0",
});

await client.connect(transport);

await client.ping();

await client.close();
await transport.close();