Five questions, each answered with a diagram. What problem MCP solves (twelve bespoke integrations become one protocol). Who the participants are (host, client, server, one client per server). What a server offers (tools, resources and prompts, and why a database server usually offers all three). What happens on the wire (four request-and-response exchanges, each carrying its own protocol version under the 2026 revision). And the three things most likely to catch you out: tutorials that predate the July 2026 specification, tool output landing in the model's context, and the fact that a tool is an offer the model may decline rather than a control.