51 pages · 5 projects · 40 things that actually broke
Five projects,
one arc.
The Model Context Protocol, taught through five projects that were actually shipped — and that were honest about their own bugs. Every number on this site came from a real run.
Each one broke the previous one's assumption
Five projects built in sequence, each a sequel that reuses the last one's code. That is what makes this a course rather than five tutorials.
- #1 · 7 pagesThe Serveroffers tools, waitsA server is a vending machine that advertises what it can do and waits.
- #2 · 7 pagesThe Hostpicks the tools, runs the loopAn "AI agent" is a
whileloop. There was never anything else in the box. - #3 · 8 pagesThe Gateasks firstA hint from the other side of a network boundary is not a permission model.
- #4 · 7 pagesThe Crewhires helpA lone agent pays again for everything it has already read, on every iteration.
- #5 · 11 pagesThe Ledgerowns the walletThe dangerous request looks exactly like the safe one on the wire.
- 🧭 …and what they add up toSix transferable lessons, and all 40 gotchas in one filterable list.
The arc
Read the labels on the arrows. Every one is a question the previous project did not know it had assumed an answer to.
✅ This is for you if
- You can write TypeScript, and have never built an MCP server.
- You want to know what Claude Desktop is actually doing.
- You are about to give an agent a tool that can delete something.
- Your agent keeps running out of room on big jobs.
- Something you connected can spend your money.
🚧 It is not
- A reference for the MCP specification — read the spec for that.
- A framework tour. There is no framework; the protocol is JSON.
- A set of best practices invented on a whiteboard. Everything here either shipped or broke, and usually both.
I just want the code
All five are public and deployed. Project #1 needs no API key and no database.
Start at “what is MCP?”, finish knowing why a refusal costs $0.00.
Start the course →