What MCP Actually Is, Once You Read the Wire Format

Sun, 30 Aug 2026 09:00:00 +0100

There is no handshake in the current MCP specification. Three requests, each carrying its own protocol version, and only the third one reaches your tool:

sequenceDiagram participant C as Client participant S as Server C->>S: server/discover S-->>C: supportedVersions, capabilities C->>S: tools/list S-->>C: name, description, inputSchema C->>S: tools/call S-->>C: content

Most explanations of the Model Context Protocol stop at “it is like USB-C for AI”. That tells you the protocol exists and nothing about what it does, which is a problem if you are about to build a server with it. I am about to build one - infra-brain, which will answer infrastructure questions from ArgoCD, Kubernetes and Grafana instead of five browser tabs - and I gave myself a week of reading before writing any code.

MCP on Lumex

What MCP Actually Is, Once You Read the Wire Format