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MPP (Machine Payments Protocol) is an open protocol for pay-per-request HTTP access. Instead of an API key, you pay a small amount of USDC on Tempo for each request — ideal for AI agents that need onchain data without managing subscriptions or key rotation. This is an alternative authorization method for the same Zerion API. Endpoints, JSON:API responses, query parameters, and filters all behave exactly as in the rest of the docs — only the way you prove access changes. Zerion also supports x402, a sibling protocol that settles on Base or Solana. See Authentication for an overview of all access methods.

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Quickstart with the Zerion CLI

The easiest way to use MPP is with the Zerion CLI, which handles the payment handshake, wallet signing, and retries automatically. Set an EVM private key for a wallet that holds USDC on Tempo, then make a request with --mpp: 
export WALLET_PRIVATE_KEY="0x..."
zerion-cli wallet portfolio 0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045 --mpp
Set ZERION_MPP=true to enable MPP globally for analytics commands instead of passing --mpp on every call. If you already use WALLET_PRIVATE_KEY for x402, the same key works for MPP — or set TEMPO_PRIVATE_KEY to use a different wallet for Tempo.

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Direct integration

If you’re not using the CLI, use one of the official MPP SDKs (TypeScript, Python, Go, Rust) to handle payment construction and retries. You’ll need a wallet with USDC on Tempo and its EVM private key.

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Example

import { privateKeyToAccount } from 'viem/accounts'
import { Mppx, tempo } from 'mppx/client'

Mppx.create({
  methods: [tempo({ account: privateKeyToAccount(process.env.WALLET_PRIVATE_KEY) })],
})

// Global fetch now handles 402 automatically
const res = await fetch(
  'https://api.zerion.io/v1/wallets/0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045/portfolio'
)
const data = await res.json()

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How it works

  Client                     Zerion API
    |                             |
    |  1. GET /v1/wallets/...     |
    | --------------------------> |
    |                             |
    |  2. 402 Payment Required    |
    | <-------------------------- |
    |     WWW-Authenticate:       |
    |     Payment <challenge>     |
    |                             |
    |  3. GET /v1/wallets/...     |
    |     Authorization:          |
    |     Payment <credential>    |
    | --------------------------> |
    |                             |
    |  4. 200 OK                  |
    |     Payment-Receipt: ...    |
    | <-------------------------- |
    |                             |
  1. Client sends a request to an API endpoint
  2. Server returns 402 with a WWW-Authenticate: Payment challenge describing where and how much to pay
  3. Client signs a USDC transfer on Tempo and retries with an Authorization: Payment header
  4. Zerion verifies the credential with the MPP facilitator and returns the response

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Rate limits

None — pay per request, no per-second or monthly quota.

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Error handling

  • 402 Payment required — no or invalid payment credential. Inspect the WWW-Authenticate: Payment response header for a fresh challenge and retry.
  • 402 MPP payment rejected — the facilitator rejected the credential. The detail field contains the reason (e.g. insufficient funds, expired authorization).