MCP Gateways vs Agent Gateways vs AI Gateways: What's the Difference and Which Do You Need?

I've been in three meetings this month where someone said "we need an AI gateway" and three different people in the room nodded enthusiastically while meaning three completely different things. One meant LLM routing (because OpenAI went down again). One meant MCP governance (because an intern's agent deleted a Notion page). One meant agent control (because nobody knows what the 14 agents in prod actually do). They were all right. They were also all talking about different products. And then...