MCP transports

MCP is transport-agnostic. The protocol works the same whether you're talking to a local subprocess over stdin or to a remote HTTPS endpoint. Picking the right transport matters for performance and security.

stdio, local subprocess

The client spawns the server as a child process and talks to it over stdin/stdout. Messages are newline-delimited JSON.

When to use:

• Local tools that need file system access
• Dev tools (git, build systems, linters)
• Anything where a network transport adds unnecessary overhead

Pros:

• No network configuration
• Process isolation (kill the server = kill access)
• Very fast (no HTTP overhead)
• Native to Claude Code and many IDE clients

Cons:

• Client must be on the same machine
• No multi-user support
• Harder to update (restart required)

SSE. Server-Sent Events

The client opens an HTTP connection to the server; the server streams events back. Good for remote servers that want long-lived bidirectional-ish communication.

When to use:

• Hosted MCP servers (someone else runs them)
• Multi-user environments (Claude.ai connectors, team deployments)
• Tools that benefit from streaming responses

Pros:

• Works across machines
• Plays nicely with HTTP infra (load balancers, TLS, auth)
• One server can serve many clients

Cons:

• More operational overhead (hosting, scaling, TLS)
• Latency (network round-trips)
• Requires auth handling you don't need locally

HTTP, request/response

Plain stateless HTTP. The client sends a JSON-RPC request, the server responds. No streaming.

When to use:

• Simple remote servers
• When streaming isn't needed
• Serverless deployments (Lambda, Workers) where long-lived connections are expensive

Pros:

• Simplest to build, simplest to host
• Works behind any HTTP infra
• Stateless, trivially scalable

Cons:

• No streaming, so slower on long tool calls
• More round-trips for multi-step interactions

Decision matrix

If the server is…	Use transport
On your machine, for your use only	stdio
Hosted, serving one user (you)	SSE or HTTP
Hosted, serving a team	SSE (for streaming) or HTTP (simpler)
Serverless (Lambda, Cloudflare Workers)	HTTP

Mixing transports

Clients can connect to many servers, each over a different transport. Claude Code happily talks to local stdio servers (git, filesystem) and remote HTTP/SSE servers (Notion, Gmail) at the same time.