testmpp

The public test endpoint for MPP — the Machine Payments Protocol. Send an agent payment, get an echo back. The free /echo verifies your HTTP plumbing for nothing; /pay/echo is live on Tempo mainnet and settles a real $0.01 USDC.e per call — so point a paying client at it only when you mean to spend.

LIVE free echo, spec-correct 402 challenges & on-chain settlement (mainnet)

Quickstart

See a real MPP challenge right now:

curl -i https://testmpp.com/pay/echo

You get 402 Payment Required with a WWW-Authenticate: Payment header — the standard MPP challenge (method tempo, intent charge, $0.01 in USDC.e on Tempo mainnet, chain 4217).

Pay it with the official MPP CLI. This spends a real $0.01 USDC.e — only run it with a funded mainnet account when you mean to:

npx mppx account create
# fund the account with real USDC.e on Tempo mainnet
npx mppx https://testmpp.com/pay/echo          # settles $0.01 USDC.e for real

Want to rehearse the full pay-and-echo loop for free? Run your own testmpp instance against Moderato testnet — set MPP_CHAIN_ID=42431 and fund from the free faucet (pathUSD, no real money).

Just want to verify your HTTP plumbing without paying anything? The free echo returns whatever you send:

curl -s https://testmpp.com/echo -d '{"hello":"agent"}' | jq

Endpoints

Full reference, including the decoded challenge format: /docs.

What is MPP?

MPP (Machine Payments Protocol) is the open protocol for machine-to-machine payments over HTTP, launched by Stripe and Tempo on March 18, 2026. It gives the long-reserved HTTP 402 Payment Required status real semantics:

1. Your agent requests a resource. The server answers 402 with a WWW-Authenticate: Payment challenge (price, currency, recipient, chain).
2. The agent pays — Tempo stablecoins, Stripe cards, or other methods — and retries with an Authorization: Payment credential.
3. The server verifies, settles, and returns the resource plus a Payment-Receipt header.

The core scheme is an IETF draft (draft-ryan-httpauth-payment-01), the spec lives at tempoxyz/mpp-specs, and it's backward-compatible with x402. If you're building agentic payments, agent commerce, or pay-per-request APIs, MPP is the rail — and testmpp is where you point your client first.

Why a test endpoint?

When agents are the ones paying, they need somewhere real to verify their payment plumbing end-to-end: does my client parse challenges? Sign credentials correctly? Handle receipts and expiry? testmpp answers that with real protocol traffic — like httpbin, but for agent payments. Start free against /echo or your own testnet instance, then prove the production rails against the live mainnet /pay/echo when you're ready to settle a real $0.01.

FAQ

Does this cost real money?

The free /echo never costs anything. /pay/echo runs on Tempo mainnet (chain 4217) with USDC.e, so a successful payment moves a real $0.01 — only point a paying client at it when you mean to spend. To test the full pay-and-echo loop for free, run your own testmpp instance against Moderato testnet (MPP_CHAIN_ID=42431) with pathUSD from the free faucet.

MPP vs x402?

x402 (Coinbase → Linux Foundation) pioneered HTTP-native stablecoin payments with a facilitator model. MPP (Stripe + Tempo) is the IETF-track HTTP 402 formalization — method-agnostic, no facilitator required, backward-compatible with x402.

What clients work?

The official mppx SDK (TypeScript, Python, Rust, Go, Ruby) and its CLI; MCP-capable agents via mppx mcp add; or raw HTTP if you build the credential yourself.