T402 API Reference - v2.8.0
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    Class A2APaymentClient

    A2A Payment Client

    Provides methods for handling t402 payments in A2A client agents.

    const client = new A2APaymentClient({
      onPaymentRequired: (req) => console.log('Payment required:', req),
    });

    // Check if task requires payment
    if (client.requiresPayment(task)) {
      const requirements = client.getRequirements(task);
      const payload = await mechanism.createPaymentPayload(requirements);
      const message = client.createPaymentMessage(payload);
      // Send message via A2A
    }
    Index

    Constructors

    constructor

    Methods

    requiresPayment getRequirements selectPaymentOption createPayload createPaymentMessage handlePayment extractEmbeddedRequirements createEmbeddedPaymentMessage

    Constructors

    Methods

    • Check if a task requires payment

      Parameters

      • task: A2ATask

      Returns boolean

    • Get payment requirements from a task

      Parameters

      • task: A2ATask

      Returns any

    • Select the best payment option from requirements

      Parameters

      • requirements: PaymentRequired

        Payment requirements with accepts array

      • OptionalpreferredNetwork: string

        Preferred network (CAIP-2 format)

      • OptionalpreferredScheme: string

        Preferred scheme (e.g., 'exact', 'upto')

      Returns any

      The best matching payment option or undefined

    • Create a payment payload using a mechanism client

      Parameters

      • mechanism: SchemeNetworkClient

        The scheme/network client to use

      • requirements: PaymentRequired

        Payment requirements to fulfill

      Returns Promise<PaymentPayload>

      Promise resolving to the payment payload

    • Create a payment submission message

      Parameters

      • payload: PaymentPayload

        The payment payload to submit

      • text: string = "Here is the payment authorization."

        Optional text message

      Returns A2AMessage

      A2A message with payment metadata

    • Handle a complete payment flow for a task

      This is a convenience method that checks for payment requirements, creates a payload, and returns a payment message.

      Parameters

      • task: A2ATask

        The A2A task that may require payment

      • mechanism: SchemeNetworkClient

        The mechanism client to use for signing

      • OptionalpreferredNetwork: string

        Optional preferred network

      • OptionalpreferredScheme: string

        Optional preferred scheme

      Returns Promise<any>

      A2A message with payment, or undefined if no payment needed

    • Extract payment requirements from an embedded-flow task. Scans task artifacts for CartMandate DataPart with x402 method data.

      Parameters

      • task: A2ATask

        The A2A task with CartMandate artifacts

      Returns PaymentRequirements[]

      x402 payment requirements or undefined

    • Create a payment message for the AP2 embedded flow. Wraps the PaymentPayload inside a PaymentMandate DataPart.

      Parameters

      • mandateContents: PaymentMandateContents

        Payment mandate contents (without payment_response)

      • payload: PaymentPayload

        The x402 payment payload

      • OptionaluserAuthorization: string

        Optional user authorization (Verifiable Presentation)

      • text: string = "Here is the payment mandate."

        Optional text message

      Returns A2AMessage

      A2A message with PaymentMandate DataPart

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