Understanding MCP Server Transports: STDIO, SSE, and HTTP Streamable

If you've been exploring Claude Code or building AI tools, you've probably heard about MCP (Model Context Protocol). But when it comes to setting up your own MCP server, one question often comes up: which transport should I use? In this article, I'll break down the three main MCP transports—STDIO, SSE, and HTTP Streamable—explain when each was introduced, what problems they solve, and help you choose the right one for your project. What is MCP? MCP (Model Context Protocol) is an open protocol that lets AI assistants like Claude connect to external tools and data sources. Think of it as a standardized way for AI to "talk" to your code. An MCP server exposes tools (functions the AI can call) and resources (data the AI can access). The transport is simply how the client (like Claude Code) communicates with your server. The Three Transports at a Glance Transport Use Case Network Complexity STDIO Local tools, scripts None (subprocess) Simple SSE Web environments, legacy HTTP Medium HTTP Str