An AI agent can turn one user request into a small storm of model calls, MCP tool calls, retries, partial failures, and background work. If you only meter the final response, you are guessing. If you meter every low-level event without context, you create noise customers will not trust. That is the billing trap many AI product builders are walking into: the product feels simple, but the usage behind it is multi-step, non-deterministic, and easy to dispute. MCP makes this more urgent. The M...