MPP Compatibility
Cross's relationship to the Machine Payments Protocol from Stripe and Tempo.
MPP (Machine Payments Protocol) is an open, IETF-tracked standard for machine-to-machine payments over HTTP. It was published in March 2026 by Stripe and Tempo, extending the x402-style request-pay-retry pattern with Stripe’s billing infrastructure and Tempo’s L1 settlement layer.
Cross is designed to be compatible with MPP-speaking clients, routing their payments through Robinhood Chain rather than Stripe/Tempo infrastructure.
How MPP relates to x402
MPP and x402 share the same core mechanic: a 402 Payment Required response signals that a resource requires payment, the client pays, and the client retries with a proof. MPP formalizes this into an IETF draft with:
- A standardized payment negotiation schema
- Defined settlement profiles (Stripe, Tempo, and potentially others)
- Structured error codes and retry semantics
Cross’s HTTP payment response is designed to be parseable by any MPP-compliant agent. The differences are at the settlement layer: where MPP routes to Stripe/Tempo, Cross routes to Robinhood Chain.
What this means for agent developers
An agent built to speak MPP (for example, one using a framework that integrates the MPP client spec) can interact with Cross-powered endpoints without code changes. The agent reads the 402 response, finds a payment scheme it understands, executes the payment, and retries. From the agent’s perspective, the settlement layer is opaque.
The only difference an MPP agent would notice is the network field in the payment object:
{
"network": "robinhood-mainnet",
"token": "EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v"
}
Versus a Stripe-backed MPP endpoint which would specify Stripe’s settlement details. If the agent has a Robinhood Chain wallet and access to the Cross Facilitator, it can pay.
What this means for service providers
If your service already accepts MPP payments via Stripe, you can add Cross as a second settlement option without changing your API structure. The Cross payment gate adds a Robinhood Chain native option to your 402 response alongside your existing Stripe option. Agents pick the one that matches their wallet.
Cross’s IETF roadmap
Cross intends to submit a Robinhood Chain native MPP settlement profile to the IETF draft alongside the Stripe/Tempo submission. This is planned for Phase 3 (Q1 2027) once the MPP specification has stabilized sufficiently for an alternative settlement profile submission.
Current status
During beta, Cross tracks MPP compatibility informally. The SDK is designed to produce and consume responses that are structurally compatible with MPP, but formal certification against the IETF draft is post-beta work. If you are building an agent framework and want to validate Cross’s MPP compatibility in your stack, reach out through the beta program.