MCP Beginner's Guide - Step by Step Tutorial

Imagine two apps trying to chat.

They already agree on what to say (JSON-RPC messages), but they still need to pick how to deliver those messages—like choosing between passing sticky-notes, talking on the phone, or jumping onto a video call.

That "how" is called a transport mechanism.

1 The Three Built-in Ways to Deliver Messages

2 How Each One Feels in Real Life

Transport	Everyday Analogy (for Western life)	When It's Great	When It's Not
stdio	Two programs sitting on the same laptop, sliding Post-it notes under the keyboard	Fast (no network) Super simple Totally private	Only works locally One client at a time
SSE (old)	A one-way radio broadcast plus a text hotline on the side	Lets a remote server "stream" data (like sports scores)	Disconnects a lot on serverless/cloud Being phased out
Streamable HTTP (new)	A Zoom link that starts with chat messages but can switch to live video	Cloud-native, easy to reconnect One URL does everything	A little more code than stdio

stdio – "Passing Sticky Notes Locally"

Setup: Your app launches the server as a child process, sends notes through stdin, reads replies from stdout.
Think: Like running a small helper script on your MacBook—no Internet, no strangers.
Use it for: Local tools that read a WhatsApp chat backup or your hard-drive files.

SSE – "Old-School Live Radio" (legacy)

Setup: Browser does GET /sse to start listening; it posts back on another URL.
Think: Live score updates: server keeps talking, you text your questions back.
Why it's fading: Cloud platforms kill idle connections; browsers cap you at ~6 streams.

Streamable HTTP – "Zoom-Style All-in-One Link"

Setup: One endpoint /mcp.
- Normal POST → instant JSON reply (like chat).
- Ask for text/event-stream in the headers → server flips to a live stream (like turning on the camera).
Extras: Server may hand you a session ID so you can drop and rejoin without losing your place—similar to re-entering a Zoom room with the same meeting ID.
Best for: Cloud functions, SaaS back ends, AI models that drip out words token-by-token (ChatGPT style).

3 Quick "Which One Should I Use?" Decision Guide

🤔 Are both client & server on the same machine?

✅ YES

⚡ Use stdio

Easy win! Fast, simple, and secure for local communication.

Recommended

❌ NO

Already running on old SSE?

👍 Yes

Keep SSE for now
But plan to migrate

👎 No

Streamable HTTP
The modern choice

🔧

Advanced Option: Need something different? You can write a custom REST transport. MCP lets you plug in anything, as long as the payload is still JSON-RPC.

4 Key Takeaways in One Breath

stdio = lightning-fast, local-only sticky notes.
SSE = legacy radio broadcast; works but creaky.
Streamable HTTP = Zoom-style "chat + stream" that loves the cloud.

Pick the channel that matches where your app lives, and your MCP messages will arrive safe and sound.