---
title: MPP (Tempo / pathUSD) — Payment
description: Same product, same price, different signing scheme — TIP-20 stablecoin via Tempo.
url: https://agentnumber.really.com/docs/payment/mpp
doc_version: "1.0.0"
last_updated: "2026-05-15"
---

> ## Documentation index
> Fetch the complete documentation index at: https://agentnumber.really.com/llms.txt
> Use this file to discover all available pages before exploring further.

# MPP (Tempo / pathUSD)

> Same product, same price, different signing scheme. MPP is the Tempo Mass Payment Protocol — TIP-20 stablecoin transfers signed as a credential on the request itself.

## How the rail works

1. [`POST /subscribe`](/docs/reference/subscribe) with no payment header → server returns `402`.
2. Read the `x-payment-info` extension on the operation in [openapi.json](/openapi.json) (see canonical shape below).
3. Build a Tempo charge credential with the [mppx SDK](https://github.com/coinbase/mppx-sdk) (or equivalent).
4. Send `Authorization: Payment <base64-credential>` on the retry.
5. Server validates with the MPP facilitator, settles, issues the bearer.

## Canonical `x-payment-info` shape

Per [mpp.dev/advanced/discovery](https://mpp.dev/advanced/discovery):

```json
"x-payment-info": {
  "amount": "1800000000",
  "currency": "0x20c0000000000000000000000000000000000000",
  "description": "One persistent US mobile number, 1-year subscription (SMS + voice).",
  "intent": "charge",
  "method": "tempo"
}
```

## Why MPP

- **Tempo-native.** If you're already on Tempo's rails, no x402 detour.
- **Single-request signing.** Credential travels in the `Authorization` header — fits the standard HTTP auth pattern.
- **Same final state.** The bearer + number you receive are interchangeable with the x402 path.

## See also

- [Payment overview](/docs/payment)
- [x402](/docs/payment/x402) — alternative rail
- [/subscribe reference](/docs/reference/subscribe) — full schema

## Sitemap

- [Overview](/docs/)
- [Quickstart](/docs/quickstart)
- [Authentication](/docs/auth)
- [SMS](/docs/sms)
- [Voice](/docs/voice)
- [MCP](/docs/mcp)
- [Payment](/docs/payment)

See the full [sitemap.md](/sitemap.md) for the complete index of docs pages.

---

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