Every major AI vendor now supports the Model Context Protocol. The framing is almost always the same: MCP is the universal connector for AI agents in the enterprise. That framing sets up a false choice. MCP, REST/HTTP APIs, and Apache Kafka are not alternatives. They solve different problems at different layers of the architecture. Treating them as competing options produces systems that are fragile exactly where they need to be reliable.These three technologies can and do coexist in the same architecture. The question is not which one to pick. It is which one belongs where, and what the tradeoffs are when more than one could technically do the job. This article maps that decision: what each technology is built for, where the boundaries are, and where the genuine gray areas lie.