Stripe Link MPP

Use these blocks to purchase from HTTP endpoints that implement the Machine Payments Protocol (MPP). The flow reads a merchant's HTTP 402 Stripe challenge, creates a Shared Payment Token spend request for the user to approve, and then retries the purchase with that token. The token is not exposed as a graph output; the pay block sends it to the guarded merchant request only inside an Authorization: Payment credential.

Stripe Link Get Payment Challenge

What it is

MPP step 1 of 3: read a merchant's HTTP 402 payment challenge to learn its network ID and amount. Step 2 is Create Spend Request with credential type 'shared_payment_token' and that network ID; step 3 is MPP Pay. Returns supports_mpp=false for ordinary merchants — use the virtual-card flow for those.

How it works

The block sends the requested method and JSON body without authentication and does not follow redirects. A guarded HTTP client rejects disallowed URLs. For a Stripe Payment challenge, the block decodes the bounded base64url request and returns its network ID, amount, and currency. A successful response without a 402 sets supports_mpp to false. A 402 with no challenge or no Stripe challenge sets payment_required to true; a selected Stripe challenge that is malformed or oversized produces an error instead. Other HTTP failures also return an error because support could not be determined.

Inputs

Input	Description	Type	Required
url	The merchant endpoint to purchase from	str	Yes
method	HTTP method the purchase uses	str	No
body	JSON body for the purchase request	Dict[str, Any]	No

Outputs

Output	Description	Type
error	Error message on failure	str
supports_mpp	True when the merchant answered 402 with a Stripe payment challenge, so a Shared Payment Token can pay it. False means it cannot be paid this way — check payment_required to see whether that is because nothing is owed or because the merchant only accepts a method this block cannot provide. A probe that got no answer at all raises instead, so it is never reported as False.	bool
payment_required	True when the merchant demanded payment (HTTP 402) but not via Stripe — an onchain-only merchant, say. With supports_mpp false this distinguishes 'pays another way, unreachable from here' from 'served without charging', where the virtual-card flow is the sensible fallback.	bool
network_id	Merchant network ID — pass this to Create Spend Request as network_id	str
amount	Amount the merchant wants, in the smallest currency unit	int
currency	Three-letter currency code	str
description	What the merchant says the charge is for	str

Possible use case

Paid API Discovery: Probe an API endpoint for a Stripe MPP challenge before constructing a payment.

Spend Request Setup: Pass network_id, amount, and currency to Create Token Spend Request when supports_mpp is true.

Unsupported Payment Routing: Stop or choose an advertised payment method when payment_required is true but MPP support is false.

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Stripe Link MPP Pay

What it is

MPP step 3 of 3: spend an approved Shared Payment Token at the merchant's endpoint. Follows Get Payment Challenge (step 1) and Create Token Spend Request (step 2). No card number and no checkout form. The token is single-use, so a failed payment needs a fresh spend request.

How it works

The block retrieves the spend request from Link and requires both an approved status and a Shared Payment Token. It then probes for the merchant's Stripe challenge without a Link payment credential and retries once with a generated Authorization: Payment credential. The probe carries caller-supplied headers other than Authorization. Redirects are disabled, and every merchant URL goes through the guarded HTTP client. paid is true only when that credential-bearing retry was attempted and returned a 2xx response.

Inputs

Input	Description	Type	Required
spend_request_id	An approved spend request created with credential type 'shared_payment_token'	str	Yes
url	The merchant endpoint to purchase from	str	Yes
method	HTTP method	str	No
body	JSON body for the purchase request	Dict[str, Any]	No
headers	Extra headers to send to the merchant	Dict[str, str]	No

Outputs

Output	Description	Type
error	Error message on failure	str
status_code	HTTP status the merchant returned	int
paid	True when the merchant accepted the credential-bearing payment request (2xx)	bool
response	Merchant's JSON response, e.g. an order or receipt	Dict[str, Any]

Possible use case

Paid API Purchase: Submit an approved token spend request to the same merchant endpoint that supplied the challenge.

Receipt Capture: Keep the merchant response as the order or receipt only when paid is true.

Failed Payment Recovery: Create and approve a new spend request after a failed payment instead of reusing the token.

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