Great breakdown of the trade-offs. The point that keeps coming back to me is the session persistence row in your security section. Most MCP discussions stop at tool discovery and composability, but the stateful session is where agents actually get stuck in production. Session expiry, rotation, and revocation is exactly the work that falls on the developer today, and it is the least documented part of the protocol. Your Walmart scenario B is a good example: fifteen tools across different teams means fifteen credential flows, and each one has its own expiry and rotation cadence. That is the real operational cost of MCP, and it is rarely captured in the latency comparison. The OAuth 2.1 note is fair too, the standard is still settling. I would add that the teams shipping agentic systems today are increasingly handling this with a dedicated identity layer that keeps credentials in a vault and gives agents scoped, short-lived sessions rather than baking OAuth into every server. Good write-up, saved the trade-off matrix.