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 with no payment header → server returns 402.
2. Read the x-payment-info extension on the operation in openapi.json (see canonical shape below).
3. Build a Tempo charge credential with the 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:

"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
• x402 — alternative rail
• /subscribe reference — full schema

llms.txt OpenAPI MCP server card x402.json mpp.json Agent card Agent skills SKILL.md sitemap.xml Glossary