Every team shipping AI agents right now quietly hits the same fork in the road, usually a few weeks into the work. You have a capability. Maybe it's your product's API, maybe it's an internal service, maybe it's a third-party integration. You want an agent to be able to use it. You have two credible paths, and they point in genuinely different directions. Path A: expose it as a tool-calling surface. The Model Context Protocol (MCP) is the current incarnation. The agent's host