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 too be used with x402Client.

The provider resolves 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.

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')