Would you let an AI agent spend $5 without asking you first?

I’ve been thinking about how agents are supposed to pay for tools.

Right now, most paid APIs and services still assume a human is setting up the account, adding a card, managing credits, and deciding what can be used. That works when the human is making every call, but it gets awkward once an agent is expected to choose and pay for a tool by itself.

For context, I’ve been testing one approach with FluxA: the user sets a budget and some limits first, then the agent can pay for approved APIs, MCP servers, or skills.

It sounds reasonable on paper, but I’m trying to understand where the failure modes are.

A few things I keep wondering about:

What happens if the agent chooses the wrong service?

Who pays for retries when the API fails after payment?

How do you stop a loop from making the same paid call repeatedly?

Can a malicious tool description or prompt injection influence what gets purchased?

Should users approve every payment, or only payments above a certain amount?

I can see the appeal of giving an agent a small spending limit, but I’m not sure I’d trust one with an open-ended balance.

Would you let an agent spend $5 automatically?

What controls would need to exist before you felt comfortable?