Understanding Its Role

The method by which MCP clients and servers exchange messages; common options include local standard input/output and HTTP-based remote connections.

Transport is the communication pathway—it does not independently represent what capabilities a service provides.

Understanding Through an Example

If an application starts a course materials service on the local machine, the client can exchange messages with it over STDIO, without needing a public URL. If the materials service is deployed in a remote environment, the application may access it using the HTTP method supported by the service, which may require authentication.

Visual explanationWhat problems each connection method solves
01Local STDIO

Client starts local service and exchanges input/output

02SSE

HTTP method where messages are pushed by service through event streams

03Streamable HTTP

Transmits streamable or regular responses via HTTP according to protocol

The name indicates the communication method, not that the application necessarily supports each one

A Deeper Look

  • STDIO: One program starts another local service, exchanging messages through standard input and output. Suitable for connections between local processes.
  • SSE: A method of pushing messages to clients via HTTP event streaming. Often used in scenarios that require continuously receiving service messages.
  • Streamable HTTP: Transmits MCP messages over HTTP, with streaming or standard responses depending on the implementation.

These names describe transport methods. They do not indicate that all applications support them, nor does putting a local command into a URL bar mean you can connect. Versions, authentication, networking, and server implementation still need to be verified separately.

What It Doesn't Tell You

Transport is not tools, resources, or permissions. STDIO is not automatically more secure, and HTTP does not automatically mean a remote service is untrustworthy—actual risks and limitations depend on the runtime environment, accounts, authorization, and service implementation.

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References

Information verified on 2026-09-13; the transport methods and configuration interfaces supported by specific applications need to be verified against the current version.