x402 is an open payment protocol for the web. It lets a digital service state its price in a standard machine-readable response, lets authorised software pay that amount, and then releases the requested result. At Edge Agents, the result is focused intelligence delivered through an API, and payment is accepted on five independent settlement rails: Base/USDC, XRPL/RLUSD, Solana/USDC, Arbitrum/USDC and Polygon/USDC.
SETTLEMENT RAILS
Five rails are accepted, and one payment settles on exactly one of them.
Every paid endpoint answers an unpaid request with a 402 that lists all 5 offers, one per rail, at the same US dollar price. A buyer's agent reads that list, keeps whichever rail it already holds funds on, and ignores the rest — it never needs a wallet on more than one. Each rail is enabled by its own separate flag and receiving address, so one rail going down or being switched off never affects the others.
BASE
Base/USDC
The rail the catalogue prices against, settled through the Coinbase-hosted x402 facilitator.
- Settlement asset
- USDC
- Network identifier
eip155:8453
XRP LEDGER
XRPL/RLUSD
The one rail with its own independent facilitator, settling in RLUSD rather than native XRP so the dollar price needs no live conversion.
- Settlement asset
- RLUSD
- Network identifier
xrpl:0
SOLANA
Solana/USDC
USDC on Solana, settled through the same multi-chain facilitator already used for Base.
- Settlement asset
- USDC
- Network identifier
solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp
ARBITRUM ONE
Arbitrum/USDC
USDC on Arbitrum One, settled through the same multi-chain facilitator as Base and sharing its address format.
- Settlement asset
- USDC
- Network identifier
eip155:42161
POLYGON POS
Polygon/USDC
USDC on Polygon PoS, settled through the same multi-chain facilitator as Base. Mainnet only -- this rail has no supported testnet configuration.
- Settlement asset
- USDC
- Network identifier
eip155:137
Machine-readable form of this same list: /v1/payment-rails and the agent catalogue. The rails advertised here are read from the same configuration that builds the 402 challenge, so the two cannot disagree.
WHAT HAPPENS
A purchase is a short web conversation.
RequestThe buyer agent asks an Edge endpoint for a specific report.
PriceThe service replies “payment required” with one offer per supported network, 5 in total.
AuthoriseThe agent checks those terms against its human-set policy, picks the one offer it can pay, and signs the payment only if they are allowed.
Verify and settleThe payment is checked and submitted to the network, normally through a facilitator.
DeliverEdge returns the requested intelligence and settlement details in the response.
WHY IT MATTERS
No subscription or manual checkout for every request.
Traditional API commerce often needs an account, contract, subscription and API key before software can use a service. x402 makes low-value, pay-per-use purchasing possible inside the normal web request.
This does not mean an agent has unlimited freedom. A safe buyer should be restricted to approved services, networks, currencies and maximum prices.
x402 is the protocol
It carries payment requirements and proof within ordinary HTTP requests. It is not itself a coin, wallet or bank account.
USDC and RLUSD are the payment assets
Edge prices these machine services in US dollars, settled on whichever of the 5 rails a buyer's agent already holds funds on. Every settlement asset is a dollar-pegged stablecoin, so the price is identical on all of them. RLUSD, not native XRP, is the XRP Ledger's settlement asset: pricing in a volatile asset would need a live price feed inside payment verification itself, the same reason every other rail settles in USDC rather than the chain's own token.
The facilitator is operational plumbing
It can verify and settle signed payments for the seller. It does not decide what an agent is allowed to buy.
The human remains accountable
The operator controls funding and policy. Edge returns decision support; it does not remove the need for appropriate human oversight.