MCP transports compared: stdio vs SSE vs streamable HTTP

Stdio (standard input/output) is the simplest and most widely supported MCP transport. The host spawns your MCP server as a child process and communicates via stdin and stdout pipes. No network is involved — everything runs locally. This makes stdio the default choice for local tools, file system access, and IDE integrations. Every MCP host supports stdio, making it the most compatible option. The downside is that the server must run on the same machine as the host.

1// claude_desktop_config.json — stdio transport example
2{
3  "mcpServers": {
4    "my-local-server": {
5      "command": "node",
6      "args": ["./dist/index.js"],
7      "env": {
8        "API_KEY": "your-key-here"
9      }
10    }
11  }
12}

Server-Sent Events (SSE) was the first HTTP-based MCP transport. It uses two HTTP endpoints: one for the client to send messages (POST) and one for the server to stream responses (GET with SSE). While functional, SSE has limitations: it requires two connections, does not support resumability natively, and is being deprecated in favor of Streamable HTTP. If you have existing SSE servers, they will continue to work, but new projects should use Streamable HTTP instead.

1// SSE transport server setup (legacy — avoid for new projects)
2import { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js";
3import { SSEServerTransport } from "@modelcontextprotocol/sdk/server/sse.js";
4import express from "express";
5
6const app = express();
7const server = new McpServer({ name: "sse-server", version: "1.0.0" });
8
9app.get("/sse", async (req, res) => {
10  const transport = new SSEServerTransport("/messages", res);
11  await server.connect(transport);
12});
13
14app.post("/messages", async (req, res) => {
15  // Handle incoming messages
16});
17
18app.listen(3001);

Streamable HTTP is the newest and recommended transport for remote MCP servers. It uses a single HTTP endpoint that supports both request-response and streaming patterns. Key advantages include stateless-friendly design (works behind load balancers), built-in session management via the Mcp-Session-Id header, and OAuth 2.1 authentication support. This is the transport to use when deploying MCP servers to cloud platforms like Vercel, Railway, or Render.

1// Streamable HTTP transport with Express
2import { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js";
3import { createMcpExpressApp } from "@modelcontextprotocol/sdk/server/express.js";
4
5const server = new McpServer({
6  name: "remote-server",
7  version: "1.0.0"
8});
9
10server.tool("hello", "Say hello", {}, async () => ({
11  content: [{ type: "text", text: "Hello from Streamable HTTP!" }]
12}));
13
14const app = createMcpExpressApp(server);
15app.listen(3000, () => {
16  console.error("MCP server running on http://localhost:3000");
17});

Here is a decision matrix to help you choose. Use stdio when your server runs locally and accesses local files, databases, or system tools. Use Streamable HTTP when your server needs to be accessed remotely, shared across teams, or deployed to the cloud. Avoid SSE for new projects — it is being deprecated. Stdio has zero latency overhead but is local-only. Streamable HTTP adds network latency but enables remote access, authentication, and horizontal scaling.

Claude Desktop and Cursor configure transports differently. For stdio, you specify a command and args in the config. For Streamable HTTP, you provide a URL. Claude Desktop stores its config at ~/Library/Application Support/Claude/claude_desktop_config.json on macOS. Cursor uses .cursor/mcp.json in your project root or ~/.cursor/mcp.json globally. If your project involves complex multi-transport setups or you need help choosing the right architecture, the RapidDev team can help you design the optimal configuration.

1// Claude Desktop — stdio transport
2{
3  "mcpServers": {
4    "local-tools": {
5      "command": "node",
6      "args": ["./my-server/dist/index.js"]
7    }
8  }
9}
10
11// Cursor — Streamable HTTP transport (.cursor/mcp.json)
12{
13  "mcpServers": {
14    "remote-api": {
15      "url": "https://my-mcp-server.railway.app/mcp"
16    }
17  }
18}