Question 1

Does send21 hold funds or private keys?

Accepted Answer

No. send21 is software that prepares payment instructions. It has no private keys, no signing code, and no broadcast path — every payment is signed and broadcast by the sender's own wallet, and funds move directly from sender to receiver.

Question 2

How can my webshop accept purchases from AI agents?

Accepted Answer

Your backend creates a payment request with one REST call (price in any of 165 world currencies, your receiving addresses, your order id). The response and pay page are machine-readable, so an AI agent can select a currency, pay from its operator's wallet, and your shop reconciles automatically via an HMAC-signed webhook carrying the order id and exact conversion rate.

Question 3

Which currencies can I price payments in?

Accepted Answer

All 165 actively used world currencies (the full ISO 4217 set) — from USD, EUR, GBP and SEK to NGN, VND and PHP. The exchange rate is locked when the payer commits and recorded with full provenance; settlement is always in BTC, USDC, USDT, or EURC directly to your own wallet.

Question 4

Which wallets can customers pay with?

Accepted Answer

Checkout pay links use one standard QR (BIP-21, Solana Pay, or EIP-681) and work with any mainstream wallet. Multi-output payment drafts need a PSBT-capable wallet such as Bitcoin Core, Sparrow, or Electrum.

Question 5

What does send21 cost?

Accepted Answer

Fees are tiered by payment size, from 0.49% on small payments down to 0.01% above $100,000, with a $0.01 minimum and $100 maximum. The schedule is public and machine-readable, the receiver always gets the exact billed amount, and the fee is never deducted from the customer's payment.

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