How do you let your AI agent pay for things without giving it your card?

We kept hitting the same wall while building with AI agents: the agent can write code, renew a subscription, or top up an API balance — but it can’t actually pay. Someone has to manually enter card details every time, which defeats the point of an “autonomous” agent.

Giving the agent your real card number feels wrong. Prepaid cards work until they don’t (limits, declines, no visibility). So we tried something different: a virtual card with per-purchase limits that stays frozen between transactions, and an MCP server so the agent can request a payment within the limit you set.

It’s called GuaraPay, and we just launched it. But I’m more interested in the general problem: if you use agents like Cursor, Claude, or ChatGPT for real work, how do you handle payments today? Do you top up manually, use a shared card, or avoid it altogether?

And a second question: what would make you trust an agent with a card at all? A hard limit? A confirmation step? Something else?

Would love to hear how others are solving this — it feels like a gap that everyone hits eventually.