x402
HTTP 402 payment protocol for machine-to-machine settlement, commonly used for paid API / agent tool calls.
Generally availablePayments & commerce railsAPI / SDK
Open protocol; settlement costs are chain / facilitator fees, not a SaaS list price.
Verified 2026-09-30
Designed for machine settlement; still review security controls
Typical tasks
- Gate an API behind pay-per-request settlement
- Let an agent pay and retry after HTTP 402
Limits & caveats
- Requires compatible wallets / facilitators
- Not a full retail checkout UX like ACP Instant Checkout
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