Here’s a clean, concise comparison of MCP’s official transports—stdio and Streamable HTTP—plus notes on custom transports.
✅ MCP Transport Comparison (Pros & Cons)
1) stdio Transport
Pros
Advantage Why It Matters Fastest + lowest latency No HTTP overhead, direct process pipes. Ideal for local tooling. Simple implementation Just read/write UTF-8 JSON lines. Automatic lifecycle management Client spawns the server subprocess—easy to track crashes, restarts. Secure by default No network exposure → no CORS, no DNS rebinding, no headers. Deterministic Each client has its own process & isolated state.
Cons
Limitation Impact Local-only Cannot connect to remote servers. No distributed topology. One client per server instance No multi-client use case (e.g., shared tools, cloud agents). Harder debugging subprocess stdout must be pure JSON; logs must go to stderr. Process management burden Client must spawn, monitor, kill the server.
Best for:
Local developer tools, CLIs, plugins, IDE integrations.
2) Streamable HTTP Transport
Pros
Advantage Why It Matters Works over network Remote MCP servers, cloud tooling, multi-user environments. Supports streaming (SSE) Real-time server→client messages, long-running operations. Multi-client capable Many clients talk to one server. Stateless or stateful sessions Session IDs enable sticky session behavior. Resumable streams with Last-Event-ID Reliable delivery across disconnects. HTTP tooling ecosystem Proxies, load balancers, auth layers, observability.
Cons
Limitation Impact More complex implementation Need to implement POST + GET, SSE, session headers, resumability. Security overhead Must handle Origin checks, auth, DNS rebinding protection. Higher latency HTTP round-trips & framing overhead. More error states Network disconnects, slow clients, streaming errors. Requires infrastructure Not great for single-user local dev tools.
Best for:
Cloud-hosted agents, shared MCP servers, multi-user products, remote integrations.
3) Custom Transports
Examples: WebSockets, gRPC, Unix domain sockets, NATS, in-memory queues.
Pros
Advantage Notes Complete flexibility Can match domain requirements (e.g., WebSockets for browser environments). Optimized for performance gRPC or UDS can exceed HTTP performance. Can bypass SSE limitations Real bidirectional streaming possible. Integrate existing infra Use your org’s transport/bus/security layer.
Cons
Limitation Impact Not standardized Client/server compatibility becomes harder. More engineering burden Must document handshake, lifecycles, streaming semantics. Must maintain JSON-RPC discipline Message framing still required. Harder for ecosystem tools Generic MCP clients may not support your custom transport.
Best for:
Deeply integrated enterprise systems, browser-only clients, high-performance environments.
🧩 Summary Table (At a Glance)
Transport Local? Remote? Multi-client Streaming Complexity Security Work Best Use stdio ✔️ ❌ ❌ Limited ⭐ Easy ⭐ Minimal Dev tools, CLIs, IDE plugins Streamable HTTP ✔️ ✔️ ✔️ SSE ⭐⭐ Medium ⭐⭐⭐ High Cloud MCP servers, multi-user tools Custom ✔️✔️ ✔️✔️ ✔️✔️ Transport-dependent ⭐⭐⭐ Hard Dependent Specialized or high-perf setups
If you want, I can also provide:
✔️ Architecture diagrams comparing them
✔️ When to choose which transport (based on your use case)
✔️ Code examples for each transport in Node/Python/Go
Just tell me.