MCP Client

An MCP client for Node.js.

[!TIP] This client has been tested with FastMCP.

Why?

• MCP TypeScript SDK provides a client for the MCP protocol, but it's a little verbose for my taste. This client abstracts away some of the lower-level details (like pagination, Zod schemas, etc.) and provides a more convenient API.
• The MCP protocol follows some REST-like naming conventions, like listTools and readResource, but those names look a bit awkward in TypeScript. This client uses more typical method names, like getTools and getResource.

Usage

Creating a client

import { MCPClient } from "mcp-client";

const client = new MCPClient({
  name: "Test",
  version: "1.0.0",
});

Connecting using stdio

await client.connect({
  type: "stdio",
  args: ["--port", "8080"],
  command: "node",
  env: {
    PORT: "8080",
  },
});

Connecting using SSE

await client.connect({
  type: "sse",
  url: "http://localhost:8080/sse",
});

Pinging the server

await client.ping();

Calling a tool

const result = await client.callTool({
  name: "add",
  arguments: { a: 1, b: 2 },
});

Calling a tool with a custom result schema

const result = await client.callTool(
  {
    name: "add",
    arguments: { a: 1, b: 2 },
  },
  {
    resultSchema: z.object({
      content: z.array(
        z.object({
          type: z.literal("text"),
          text: z.string(),
        }),
      ),
    }),
  },
);

Listing tools

const tools = await client.getAllTools();

Listing resources

const resources = await client.getAllResources();

Reading a resource

const resource = await client.getResource({ uri: "file:///logs/app.log" });

Getting a prompt

const prompt = await client.getPrompt({ name: "git-commit" });

Listing prompts

const prompts = await client.getAllPrompts();

Setting the logging level

await client.setLoggingLevel("debug");

Completing a prompt

const result = await client.complete({
  ref: { type: "ref/prompt", name: "git-commit" },
  argument: { name: "changes", value: "Add a new feature" },
});

Listing resource templates

const resourceTemplates = await client.getAllResourceTemplates();

Receiving logging messages

client.on("loggingMessage", (message) => {
  console.log(message);
});

[!NOTE] Equivalent to setNotificationHandler(LoggingMessageNotificationSchema, (message) => { ... }) in the MCP TypeScript SDK.