Machine Payments Protocol (MPP)

MPP (Machine Payments Protocol) is one of two machine-payment protocols the WAVE gateway accepts — the other is x402, which MPP is designed to interoperate with. No WAVE account or API key is required: call a route, read its 402 challenge, pay it, retry with the payment credential header.

The 402 challenge returned by the route you are calling is the authoritative source of payment terms. This page — and the discovery documents it's grounded in — is a map of what's possible; the live challenge on the route is what you actually pay.

Discovery

GET https://gateway.wave.online/.well-known/payments.json
GET https://gateway.wave.online/.well-known/x402          # x402's "mpp" field points here too

Both are unauthenticated GETs that return the full protocol list this gateway accepts — "a protocol not listed there is not implemented by WAVE."

The MPP challenge

Field	Value
HTTP status	`402`
Credential header	`Authorization: Payment`
Credential encoding	base64 JSON `MppCredential`
Intents	`charge`, `session`
Facilitator	`https://gateway.wave.online/v1/mpp/facilitator`
Verify endpoint	`https://gateway.wave.online/v1/mpp/facilitator/verify`
Settle endpoint	`https://gateway.wave.online/v1/mpp/facilitator/settle`
Supported endpoint	`https://gateway.wave.online/v1/mpp/facilitator/supported`
Spec	mpp.dev

Payment rails

MPP is rail-agnostic — the discovery document reports which settlement rails are actually wired up today. Read GET /v1/mpp/facilitator/supported before you build against one:

Rail	Status
`tempo`	live
`stripe`	live
`link-spt`	live
`base-usdc`	unconfigured
`proof`	not implemented
`lightning`	not implemented

Rail status changes independently of this page — /v1/mpp/facilitator/supported is the live source, this table is a snapshot.

Client libraries

The MPP spec lists reference client implementations: mppx (TypeScript), pympp (Python), mpp-rs (Rust). None are WAVE-published packages — they're generic MPP clients any MPP-speaking facilitator works with, WAVE's included.