x402 payments

Overview

Every scaffolded Agent includes x402 payment infrastructure—Coinbase's HTTP 402 payment protocol.

Enabling/disabling

By default, x402 payments are disabled. This is how you can enable them:

• When creating a new Agent, choose Enable x402 payments.
• After creating an Agent, run /config and select Payments.
• You can also directly edit x402 parameters in the .env file.

note

When x402 are enabled, the frontend displays a button for connecting to Metamask.

After this, you can temporarily disable x402 payments for testing purposes:

• Start the Agent with X402=false npm start
• Remove all X402_<PREFIX>_PAY_TO values from the .env file

tip

Alternatively, you can keep API key authentication enabled and bypass payments in the chat mode.

Parameters

When enabling x402 payments, you need to specify x402 parameters, which are stored in the .env file. Each payment network has its own set of variables, differentiated by prefixes.

Name	Variable	Description
Network	X402_<PREFIX>_NETWORK	The network for receiving payments, identified by ID. For development, use test chains: they require no real funds. See the supported networks.
Wallet	X402_<PREFIX>_PAY_TO	Your EVM wallet address for receiving payments (0x + 40 hex characters).
Price	X402_<PREFIX>_PRICE	The preferred price per request. It's set in USDC and defaults to 0.01. Removing this value disables the corresponding network.
Facilitator	X402_FACILITATOR_URL	The preferred facilitator for processing payments. Warden Code automatically enables one of the default facilitators, but you can edit this value in the .env file.

Networks

The available payment networks are listed below.

Each network has its own set of parameters in the .env file, differentiated by prefixes, and the default facilitator.

Network	ID	Currency	Facilitator	Prefix
Base Sepolia (testnet)	eip155:84532	test USDC	x402.org	X402_BASE_SEPOLIA
Base (mainnet)	eip155:8453	real USDC	PayAI	X402_BASE

You can find all networks with their parameters .env.example:

X402_FACILITATOR_URL=https://x402.org/facilitator

# Base Sepolia (testnet)
X402_BASE_SEPOLIA_PAY_TO=
X402_BASE_SEPOLIA_PRICE=0.01
X402_BASE_SEPOLIA_NETWORK=eip155:84532

# Base (mainnet)
# X402_BASE_PAY_TO=
# X402_BASE_PRICE=0.01
# X402_BASE_NETWORK=eip155:8453

Facilitators

A payment facilitator is a service that handles verifying and submitting x402 payments.

When you enable x402, Warden code automatically selects one of the following facilitators (based on the network):

• Testnets: x402.org
• Mainnets: PayAI

The PayAI facilitator offers 1,000 free settlements per month. For higher volumes, create a merchant account at merchant.payai.network and add the following variables to your .env file:

• PAYAI_API_KEY_ID
• PAYAI_API_KEY_SECRET

note

Authentication is handled automatically by the @payai/facilitator package when the facilitator URL contains payai.network.

Dependencies

When x402 is enabled, the following packages are added to the generated Agent's dependencies:

• express and @types/express
• @x402/express (payment middleware)
• @x402/core (protocol types and facilitator client)
• @payai/facilitator (facilitator authentication)
• @x402/evm (EVM payment scheme verification)

Payment flow

Clients that support x402 (such as @x402/fetch) handle the payment flow automatically:

1. The server returns a HTTP 402 response with payment requirements.
2. The client signs a USDC transaction.
3. The server verifies the payment before processing the request.