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Last updated: June 10, 2026
Use this guide to build a custom ChatGPT app that accepts payments using the Agentic Commerce Protocol (ACP) and the ChatGPT Apps SDK. This guide walks you through configuring Braintree as your payment provider, processing delegated payment tokens, and testing your integration.
complete_checkout tool to receive tokens.requestCheckout() from the app to trigger Instant Checkout.braintree as your payment provider.This guide does not tell you how to build a ChatGPT app. The following tips and resources, however, could help.
When your ChatGPT app widget calls requestCheckout(), you must construct a checkout session that specifies Braintree as the payment provider according to the ACP Agentic Checkout Specification.
requestCheckout()const checkoutRequest = {
id: checkoutSessionId,
payment_provider: {
provider: "braintree",
merchant_id: "your_braintree_merchant_id",
supported_payment_methods: ["card", "applepay", "googlepay"],
},
status: "ready_for_payment",
currency: "USD",
totals: [
{
type: "total",
display_text: "Total",
amount: 330, // Amount in cents
},
],
links: [
{ type: "terms_of_use", url: "https://yoursite.com/terms" },
{ type: "privacy_policy", url: "https://yoursite.com/privacy" },
],
payment_mode: "live", // Use "test" for testing with test cards
};
// Open Instant Checkout UI in ChatGPT
const order = await window.openai.requestCheckout(checkoutRequest);| Parameter | Description |
|---|---|
id | Unique checkout session identifier |
payment_provider.provider | Identify Braintree as the payment provider (braintree). |
payment_provider.merchant_id | Your Braintree public merchant ID |
payment_provider.supported_payment_methods | An array of payment methods that your Braintree integration supports. Current supported values are: card applepaygooglepay |
status | Set to ready_for_payment to indicate that the checkout session is ready to accept payment. |
currency | The ISO 4217 currency code for the transaction (for example, USD). |
totals | An array of line items for the transaction, showing the amounts in cents. |
payment_mode | Set to live for production environments or test for testing. |
For more information, see the Apps SDK Monetization Guide.
To complete checkout, your MCP server must expose a complete_checkout tool that receives the token and processes it.
Use the payment method nonce exactly as you would use any payment method nonce in Braintree's transaction.sale method or chargePaymentMethod GraphQL mutation.
The following example uses Python.
@tool(description="Complete checkout and process payment")
async def complete_checkout(
self,
checkout_session_id: str,
buyer: Buyer,
payment_data: PaymentData,
) -> types.CallToolResult:
# Extract the delegated payment token
token = payment_data.token
# Process payment using Braintree SDK
result = gateway.transaction.sale({
"amount": "10.00",
"payment_method_nonce": token,
"options": {
"submit_for_settlement": True
}
})
if result.is_success:
return types.CallToolResult(
content=[],
structuredContent={
"id": checkout_session_id,
"status": "completed",
"currency": "USD",
"order": {
"id": result.transaction.id,
"checkout_session_id": checkout_session_id,
"permalink_url": f"https://yoursite.com/orders/{result.transaction.id}",
},
},
isError=False,
)
else:
# Return error response
return types.CallToolResult(
content=[{
"type": "text",
"text": f"Payment failed: {result.message}"
}],
isError=True,
)The payment token in payment_data.token (for example,
"tokencc_bf_abc123_456def_ghijkl_mno789_pqr") is a one-time-use token that
you can process using your existing Braintree integration to complete the
payment. In Braintree, this type of token is called a payment method
nonce.
It serves as a secure, single-use reference to the buyer's payment
information. It's bound to your merchant ID and includes amount and time
restrictions that you can configure.
To test Instant Checkout in a ChatGPT App, extend your MCP server to render a widget in the ChatGPT application by completing these steps.
This step depends on your implementation. For example, if you want your application to display a Buy Now product card when someone prompts ChatGPT with something like "I want to buy wireless headphones," you would build a front-end application that reads ChatGPT's input and renders the Buy Now product card. Then, you register that HTML as a resource for the complete_checkout tool in your MCP server, as shown in the following example.
const widgetHTML = loadWidgetHTML();
const buyProductTemplateUri = "ui://widget/buy-product-template.html";
mcpServer.registerResource(
"buy-product-widget",
buyProductTemplateUri,
{
title: "Buy Product",
description: "Buy Product Widget",
mimeType: "text/html+skybridge",
},
async (uri) => ({
contents: [
{
uri: uri.href,
mimeType: "text/html+skybridge",
text: widgetHTML,
},
],
}),
);Your widgetHTML variable references the result of reading an HTML file. This guide does not require you to use any specific coding language or framework. These choices are up to you or your selected integrator.
After you register your tool, you must register the complete_checkout tool to use that resource. The following example is a tool that retrieves product information and returns it in the structuredContent field. ChatGPT attaches this response to window.openapi.toolOutput for your application to read and render.
mcpServer.registerTool(
"show-buy-product-widget",
{
title: "Buy Product",
description: "Shows the Buy Now Product Widget",
inputSchema: {
// Your integration should use a library like Zod or JSON Schema here.
product_title: string,
},
_meta: { "openai/outputTemplate": buyProductTemplateUri },
annotations: { readOnlyHint: true },
},
async (input) => {
//This is just an example, your application can retrieve product information in anyway you see fit
const product = await productService.findByTitle(input.product_title);
return {
content: [],
structuredContent: {
...product,
},
_meta: {
"openai/outputTemplate": widgetHTML,
},
};
},
);To initiate checkout from your ChatGPT app, call window.openai.requestCheckout, typically using a button. When ChatGPT initiates checkout, your server's /checkout_sessions response must specify Braintree as the payment provider according to the ACP agentic checkout specification, as shown in the following example.
{
"payment_provider": {
"provider": "braintree",
"supported_payment_methods": ["card"],
"merchant_id": "your_braintree_merchant_id"
}
}| Parameter | Description |
|---|---|
payment_provider.provider | Payment provider. Set to braintree. |
payment_provider.supported_payment_methods | An array of payment methods that your Braintree integration supports. Available values are: cardapplepaygooglepay Other options, including these, are coming soon: paypal_walletvenmo_wallet |
merchant_id | Your Braintree merchant ID, which identifies your Braintree account. |
OpenAI uses the merchant_id that you provide here in the
allowance.merchant_id field when it requests delegated payment tokens.
After you host your MCP server with a publicly available URL, test your application in ChatGPT's developer mode.
Now you can go to the ChatGPT prompt screen, click the plus (+) symbol, select your application, and enter the prompt to display your widget.
Braintree validates the following fields in the allowance when issuing a delegated payment token.
merchant_idThe merchant_id must match the Braintree public merchant ID that processes the transaction.
{
"message": "Unknown or expired single-use payment method.",
"path": ["chargePaymentMethod"],
"extensions": {
"errorClass": "VALIDATION",
"errorType": "user_error",
"inputPath": ["input", "paymentMethodId"],
"legacyCode": "91565"
}
}max_amountThe max_amount must be greater than or equal to the transaction amount.
{
"message": "Transaction amount exceeds the payment method maximum amount.",
"path": ["chargePaymentMethod"],
"extensions": {
"errorClass": "VALIDATION",
"errorType": "user_error",
"inputPath": ["input", "transaction", "amount"],
"legacyCode": "915266"
}
}currencyThe currency on the transaction must match the configured currency for the transacting merchant.
{
"message": "Transaction currency does not match the payment method currency.",
"path": ["chargePaymentMethod"],
"extensions": {
"errorClass": "VALIDATION",
"errorType": "user_error",
"inputPath": ["input", "transaction", "merchantAccountId"],
"legacyCode": "915267"
}
}expires_at{
"message": "Unknown or expired single-use payment method.",
"path": ["chargePaymentMethod"],
"extensions": {
"errorClass": "VALIDATION",
"errorType": "user_error",
"inputPath": ["input", "paymentMethodId"],
"legacyCode": "91565"
}
}PayPal and Braintree provide the following ways to track AI-initiated transactions.
When you process a transaction with a delegated payment token, it includes the following fields in the transaction response.
transaction.facilitator_details.oauth_application_client_id
transaction.facilitator_details.oauth_application_name # "ChatGPT"For example, your transaction response might look similar to this one.
result = gateway.transaction.find("transaction_id")
puts result.transaction.facilitator_details.oauth_application_name
# => "ChatGPT"
puts result.transaction.facilitator_details.oauth_application_client_id
# => "oauth_client_abc123"You can search for transactions by AI platform using the Braintree Control Panel or API.
facilitator_details.oauth_application_name.ChatGPT to view all ChatGPT-initiated transactions. query($input: TransactionSearchInput!) {
search {
transactions(input: $input) {
edges {
node {
id
amount { value }
}
}
}
}
}