x402 API reference

The following API methods are related to x402 to create payments using delegationDelegation The ability for a MetaMask smart account to authorize another account to perform specific executions on its behalf..

createx402DelegationProvider

Creates a delegation provider function to be used with x402Erc7710Client.

The provider creates an open delegationOpen delegation A delegation that leaves the delegate unspecified, allowing any account to redeem it., signs it, and returns an ABI-encoded delegation chain as a hex string. The provider internally appends redeemer, payee, and expiry caveatsCaveat A restriction attached to a delegation that limits how delegated authority can be used. when the existing caveats, or the root delegationRoot delegation The first delegation in a chain, where an account delegates its own authority directly. doesn't have it.

When both redeemers.addresses and facilitatorAddresses from the server's payment requirements are provided, the provider resolves redeemers as the intersection of the two lists. If only one is provided, that list is used. An error is thrown if the resolved list is empty.

Parameters

Name	Type	Required	Description
account	MaybeDeferred <Account>	Yes	The Viem Account that signs the delegationDelegation The ability for a MetaMask smart account to authorize another account to perform specific executions on its behalf..
environment	MaybeDeferred <SmartAccountsEnvironment>	No	Environment to resolve the smart contracts for the current chain. If omitted, resolved automatically from the chain ID in the payment requirements.
from	MaybeDeferred <Hex>	No	The address that is granting the delegationDelegation The ability for a MetaMask smart account to authorize another account to perform specific executions on its behalf.. The default is account.
salt	MaybeDeferred <Hex>	No	The salt for generating the delegation hash. The default is a random 32-byte value.
caveats	MaybeDeferred <Caveats>	No	CaveatsCaveat A restriction attached to a delegation that limits how delegated authority can be used. that further refine the authority granted by the delegationDelegation The ability for a MetaMask smart account to authorize another account to perform specific executions on its behalf.. redeemer, allowedTargets, and timestamp caveats are auto-appended if not already present.
parentPermissionContext	MaybeDeferred <PermissionContext>	No	Parent chain as Hex or as decoded Delegation values (leaf first). Use this when creating a redelegationRedelegation A delegation that passes on authority granted by a previous delegation..
expirySeconds	MaybeDeferred <number>	No	Relative expiry in seconds. Adds a timestamp caveat if no tighter constraint exists.
redeemers	MaybeDeferred <RedeemersConfig>	No	Constrains the addresses that are allowed to redeem the delegationDelegation The ability for a MetaMask smart account to authorize another account to perform specific executions on its behalf.. Use this to restrict redemption to specific facilitators.

Example

Delegation

import { privateKeyToAccount } from 'viem/accounts'
import { createx402DelegationProvider } from '@metamask/smart-accounts-kit/experimental'
import { x402Erc7710Client } from '@metamask/x402'

const account = privateKeyToAccount(privateKey)

const erc7710Client = new x402Erc7710Client({
  delegationProvider: createx402DelegationProvider({
    account,
  }),
})

Redelegation

import { createx402DelegationProvider } from '@metamask/smart-accounts-kit/experimental'

const parentPermissionContext = '0x...' // Previously stored/issued permission context.

const delegationProvider = createx402DelegationProvider({
  account,
  parentPermissionContext,
})

parseEip155ChainId

Parses an EIP-155 CAIP network identifier into a numeric chain ID.

Parameters

Name	Type	Required	Description
network	string	Yes	EIP-155 CAIP network identifier. For example, eip155:1.

Example

import { parseEip155ChainId } from '@metamask/smart-accounts-kit/experimental'

// Returns 137
const chainId = parseEip155ChainId('eip155:137')