ACK Payment Protocol (ACK-Pay) TypeScript SDK

Agent-Native Payments Protocol for the Agent Economy

The Agent Commerce Kit Payment Protocol (ACK-Pay) TypeScript SDK provides tools for creating verifiable payment requests and receipts using W3C Verifiable Credentials.

ACK-Pay is part of the Agent Commerce Kit.

Installation

npm i @agentcommercekit/ack-pay
# or
pnpm add @agentcommercekit/ack-pay

Usage

Creating a Payment Request

import { createPaymentRequestBody } from "@agentcommercekit/ack-pay"
import { createDidWebUri } from "@agentcommercekit/did"
import { createJwtSigner, curveToJwtAlgorithm } from "@agentcommercekit/jwt"
import { generateKeypair } from "@agentcommercekit/keys"

// Create a payment request
const paymentRequest = {
  id: "payment-123",
  description: "Access to premium content",
  paymentOptions: [
    {
      id: "option-1",
      amount: new BigInt(100_000_000).toString(), // 100 USDC
      decimals: 6,
      currency: "USDC",
      recipient: "did:web:payment.example.com",
      paymentService: "https://pay.example.com"
    }
  ]
}

const keypair = await generateKeypair("secp256k1")

// Create a payment request body with a signed token
const paymentRequestBody = await createPaymentRequestBody(paymentRequest, {
  issuer: createDidWebUri("https://server.example.com"),
  signer: createJwtSigner(keypair),
  algorithm: curveToJwtAlgorithm(keypair.curve)
})

// Create a 402 Payment Required response
const response = new Response(JSON.stringify(paymentRequestBody, {
  status: 402,
  contentType: "application/json"
})

Creating a Payment Receipt

import { createPaymentReceipt } from "@agentcommercekit/ack-pay"

const receipt = createPaymentReceipt({
  paymentRequestToken: "<payment-token-from-request>",
  paymentOptionId: "<payment-option-id-from-request>",
  issuer: "did:web:receipt-service.example.com",
  payerDid: "did:web:customer.example.com",
})

Verifying a Payment Receipt

import { verifyPaymentReceipt } from "@agentcommercekit/ack-pay"
import { getDidResolver } from "@agentcommercekit/did"

const verified = await verifyPaymentReceipt(receipt, {
  resolver: getDidResolver(),
  trustedIssuers: ["did:web:merchant.example.com"],
})

Type Guards for Validation

import { isPaymentRequest } from "@agentcommercekit/ack-pay"

// Check if a value is a valid payment request
isPaymentRequest(unknownObject)

// Check if a credential is specifically a payment receipt credential
isPaymentReceiptCredential(credential)

// Check if a credential subject has the payment receipt claim structure
isPaymentReceiptClaim(credential.credentialSubject)

API Reference

Payment Requests

• createPaymentRequestBody(params, options) - Creates a payment request with a signed JWT token
• isPaymentRequest(value) - Type guard for payment requests

Payment Request Tokens

• createPaymentRequestToken(paymentRequest, options) - Creates a signed JWT token for a payment request
• verifyPaymentRequestToken(token, options) - Verifies a payment request token JWT

Payment Receipts

• createPaymentReceipt(params) - Creates a verifiable credential receipt
• verifyPaymentReceipt(receipt, options) - Verifies a payment receipt credential
• getReceiptClaimVerifier() - Returns a claim verifier for payment receipts

Schema Validation

// Zod v4 schema

// Valibot schema
import { paymentRequestSchema } from "@agentcommercekit/ack-pay/schemas/valibot"
// Zod v3 schema
import { paymentRequestSchema } from "@agentcommercekit/ack-pay/schemas/zod/v3"
import { paymentRequestSchema } from "@agentcommercekit/ack-pay/schemas/zod/v4"

Agent Commerce Kit Version

This SDK supports Agent Commerce Kit version 2025-05-04.

See the ACK Versioning documentation for more information.

License (MIT)

Copyright (c) 2025 Catena Labs, Inc.