MCP and AI basics
Transport
How a client and server exchange messages. MCP defines stdio (a local process on your machine) and Streamable HTTP (a remote server over the web). Older remote servers used HTTP with Server-Sent Events.
The transport is how an MCP client and server exchange messages. The protocol defines two: stdio, where the host starts the server as a local process and talks to it through standard input and output, and Streamable HTTP, where the server is a web endpoint reached over HTTPS. Earlier remote servers used HTTP with Server-Sent Events, and some clients still accept that form.
The transport decides where a server can be used. Stdio servers need a client that can launch processes, which means desktop apps, IDEs and terminals rather than a browser tab. Streamable HTTP servers can be added to web assistants by URL and usually sign in with OAuth. The directory and the installation guides state the transport for each server.
It also decides where credentials live. With stdio, the API key or token sits on the machine running the server. With a hosted server, the vendor holds the connection and you authorise it through a sign-in screen, which is easier to revoke.