When your agent needs to spend more than you told it to

You deploy a research agent with a $100 budget. The task is competitive landscape analysis: a few market reports, some API calls, a handful of web lookups. $100 is plenty. Three weeks later, the scope changes. You need licensing data across 40 markets instead of 5. Same agent, same task, fundamentally different cost. Doing it properly runs $800. What happens next depends entirely on how you set the budget. If you hardcoded a ceiling, the agent stops midway and you get a partial result. If you didn't, it proceeds and you find out when you check your Stripe dashboard. Neither outcome is what you wanted. What you actually wanted was for the agent to ask you first. That gap (between "agent has a spending limit" and "agent can request authorization before exceeding it") is the problem Stripe's Machine Payments Protocol (MPP) exposes but doesn't solve. What MPP actually does MPP is an open standard for agent-to-service payments. The flow is simple: an agent requests a resource, the service r