How AI agents pay: AP2 for authorization, ACP for checkout, x402 for per-request, MPP for sessions
Unhappy-Life8236 · reddit · 2026-10-02
A Reddit write-up maps how four protocols fit together for AI agent payments:
- AP2 handles authorization: humans set the agent's spending cap, merchants record the mandate; nothing moves until it's in place.
- ACP handles checkout: agents send the cart as clean data through regular cards and payment networks — no merchant-side changes.
- x402 handles pay-per-request: a 402 status with a price tag, the agent's wallet signs a USDC transfer and retries; no accounts or API keys, ideal for selling API hits.
- MPP handles high-frequency calls: open a session, accumulate charges, settle at the end.
Typical flow: AP2 first for human approval, then ACP/x402/MPP depending on workflow. The overlooked gap: protocols handle payment but not post-hoc agent-level usage tracking and human-readable invoicing.
Related event: How AI Agents Pay: AP2, ACP, x402 and MPP Explained(2 posts)→
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