Connecting to MCP Servers

Learn how to connect to local and remote MCP servers

The MCPClientManager is your gateway to MCP servers. It handles connections, manages multiple servers, and provides a unified interface for calling tools, reading resources, and accessing prompts.

When to Use MCPClientManager

Use MCPClientManager when you need to:

• Connect to one or more MCP servers
• Execute tools programmatically (without an LLM)
• Build applications that aggregate tools from multiple servers
• Set up test environments for your MCP server

Two Types of Servers

MCP servers come in two transport types:

STDIO Servers (Local)

STDIO servers run as subprocesses on your machine. You provide a command and arguments, and the SDK spawns the process.

import { MCPClientManager } from "@mcpjam/sdk";

const manager = new MCPClientManager({
  myServer: {
    command: "node",
    args: ["./my-server.js"],
    env: {
      API_KEY: process.env.MY_API_KEY,
    },
  },
});

Best for:

• Local development
• Servers you’re building
• CLI-based MCP servers
• Servers requiring local resources

HTTP Servers (Remote)

HTTP servers connect via SSE (Server-Sent Events) or Streamable HTTP over the network.

const manager = new MCPClientManager({
  asana: {
    url: "https://mcp.asana.com/sse",
    requestInit: {
      headers: {
        Authorization: `Bearer ${process.env.ASANA_TOKEN}`,
      },
    },
  },
});

Best for:

• Production MCP servers
• Third-party integrations (Asana, Slack, etc.)
• Shared team servers
• Serverless deployments

HTTP Authentication Options

For HTTP servers, MCPClientManager supports three auth patterns:

• accessToken for a static bearer token
• refreshToken + clientId for non-interactive OAuth token exchange with automatic refresh
• authProvider when you need to provide a custom MCP SDK OAuth provider

If you already have a refresh token, you can let the SDK handle access token exchange and refresh for you:

const manager = new MCPClientManager({
  asana: {
    url: "https://mcp.asana.com/mcp",
    refreshToken: process.env.ASANA_REFRESH_TOKEN!,
    clientId: process.env.ASANA_CLIENT_ID!,
    clientSecret: process.env.ASANA_CLIENT_SECRET,
  },
});

With this configuration, the SDK:

• exchanges the refresh token for an access token during connection
• automatically retries with a fresh access token when the server returns an auth challenge
• stores rotated refresh tokens returned by the authorization server

refreshToken is only supported for HTTP servers. When you use it, do not also set accessToken, authProvider, or an Authorization header in requestInit.headers.

Connecting and Disconnecting

After configuring servers, you must explicitly connect:

// Connect to a specific server
await manager.connectToServer("myServer");

// Now you can use it
const tools = await manager.listTools("myServer");
console.log("Available tools:", tools.tools.map((tool) => tool.name));

// Always disconnect when done
await manager.disconnectServer("myServer");

Always disconnect servers when you’re done, especially in tests. This cleans up subprocess handles and network connections.

Working with Multiple Servers

A key strength of MCPClientManager is managing multiple servers simultaneously:

const manager = new MCPClientManager({
  math: {
    command: "npx",
    args: ["-y", "@modelcontextprotocol/server-everything"],
  },
  asana: {
    url: "https://mcp.asana.com/sse",
    requestInit: {
      headers: { Authorization: `Bearer ${token}` },
    },
  },
  github: {
    url: "https://mcp.github.com/sse",
    requestInit: {
      headers: { Authorization: `Bearer ${ghToken}` },
    },
  },
});

// Connect to all
await Promise.all([
  manager.connectToServer("math"),
  manager.connectToServer("asana"),
  manager.connectToServer("github"),
]);

// Aggregate tools from all servers
const allTools = await manager.getTools();
// Now allTools contains tools from math, asana, and github

Executing Tools Directly

You can call tools without involving an LLM—useful for unit tests:

// Direct tool execution
const result = await manager.executeTool("math", "add", { a: 5, b: 3 });
console.log(result); // 8

// Test your server's tools deterministically
expect(result).toBe(8);

Integration with TestAgent

The most common pattern is connecting servers, then creating a TestAgent with their tools:

const manager = new MCPClientManager({
  myServer: { command: "node", args: ["./server.js"] },
});

await manager.connectToServer("myServer");

// Get tools for TestAgent
const tools = await manager.getTools();

// Create agent with those tools
const agent = new TestAgent({
  tools,
  model: "anthropic/claude-sonnet-4-20250514",
  apiKey: process.env.ANTHROPIC_API_KEY,
});

// Now prompt the agent
const result = await agent.prompt("Add 2 and 3");

Error Handling

Connection failures throw errors. Wrap in try/catch for production code:

try {
  await manager.connectToServer("myServer");
} catch (error) {
  console.error("Failed to connect:", error.message);
  // Handle gracefully - maybe fall back to another server
}

Health Checks

Verify a server is responsive:

try {
  manager.pingServer("myServer");
} catch {
  console.warn("Server not responding, reconnecting...");
  await manager.disconnectServer("myServer");
  await manager.connectToServer("myServer");
}

Next Steps

Testing with LLMs

Connect LLMs to your MCP tools

MCPClientManager Reference

Full API documentation