Every time you write a bespoke AI tool integration without a standard, you're making a promise to your future self: I will maintain this forever, or I will rewrite it later.
You're not going to maintain it. And "later" has a way of arriving at the worst possible moment.
Asimov's Three Laws of Robotics encoded a philosophy about how robots should relate to humans. They weren't just rules, they were a framework for reasoning about harm, autonomy, and control. The laws conflicted with each other by design, forcing a hierarchy.
MCP's three primitives, Tools, Resources, and Prompts, encode a similar philosophy. They're not just API categories. They're a framework for reasoning about how AI should interact with the world: what it can change, what it can only read, and what humans explicitly invoke.
Get them right, and your MCP server is intuitive, safe, and composable. Get them wrong, and you'll wonder why the AI keeps calling the wrong thing at the wrong time.