MPP (Merchant Payment Protocol)

Overview

MPP lets an agent present a virtual payment card (via Stripe Issuing, Tempo, or similar) to a seller's priced endpoint. Custena authorises the card, captures on successful response, and reconciles the settlement into the seller's ledger.

It's the bridge protocol: sellers who accept Custena can be paid by agents whose spending is controlled by a corporate card program — no crypto, no platform-balance top-up required.

Flow

POST /tools/generate-image HTTP/1.1
Host: seller.example.com
X-MPP-Card: tok_visa_4242...
X-MPP-Expires: 01/28
X-MPP-CVC: 123
Content-Type: application/json

{ "prompt": "..." }

Custena intercepts, places a card authorization, forwards the call, captures on 2xx, voids on error.

Use cases

• Procurement-controlled agents — the card program is the governance layer (spending limits, categories, auditable statements)
• Cross-protocol interoperability — a non-crypto buyer reaching a non-crypto seller without custody risk on either side
• Regulated environments — card rails are a well-understood compliance surface

Settlement

• Capture happens at response time (not at authorization)
• Failed upstream → void authorization → no charge
• Fees: interchange + Custena's thin margin, passed through transparently