Head to head · Agent payment protocols · October 2026 research run
Machine Payments Protocol (MPP) vs x402
Machine Payments Protocol (MPP) has a score of 81.1 (A) against x402's 79.7 (A). Both do agent payment protocols. The largest gap is transparency & trust, 20 points.
Machine Payments Protocol (MPP)Tempo and Stripe · Payment protocol
A81.1/100graded, not ranked against tools
x402x402 Foundation (Linux Foundation) · Payment protocol
A79.7/100graded, not ranked against tools
Which one, for what
Pick Machine Payments Protocol (MPP) for
- agent ergonomics (+7)
- security & auth (+12)
Pick x402 for
- transparency & trust (+20)
Score by category
| Category | Weight this run | Machine Payments Protocol (MPP) | x402 | Edge |
|---|---|---|---|---|
| Reliability | 16%20 | 85 | 87 | x402 +2 |
| Performance | 10%pending | pending | pending | not scored in this run |
| Schema & documentation | 13%16.2 | 89 | 86 | Machine Payments Protocol (MPP) +3 |
| Agent ergonomics | 13%16.2 | 91 | 84 | Machine Payments Protocol (MPP) +7 |
| Security & auth | 14%17.5 | 79 | 67 | Machine Payments Protocol (MPP) +12 |
| Payments & pricing | 10%12.5 | 94 | 97 | x402 +3 |
| Task success | 10%pending | pending | pending | not scored in this run |
| Maintenance & community | 7%8.8 | 95 | 93 | Machine Payments Protocol (MPP) +2 |
| Transparency & trust | 7%8.8 | 45 | 65 | x402 +20 |
| Negative events | ≤15 | -3 | -3 | |
| Total | 81.1 · A | 79.7 · A |
Facts side by side
| Fact | Machine Payments Protocol (MPP) | x402 |
|---|---|---|
| Kind | Payment protocol | Payment protocol |
| Vendor | Tempo and Stripe | x402 Foundation (Linux Foundation) |
| Hosted endpoint | no (local only) | no (local only) |
| Transports | ||
| Auth | None | None |
| Pricing | Free | Free |
| x402 | no | no |
| Licence | CC0-1.0 (spec) | Apache-2.0 |
| Tools exposed | none | none |
| Context cost (tools/list) | n/a | n/a |
| p95 latency | not measured yet | not measured yet |
| Availability (30d) | not measured yet | not measured yet |
| Read-only variant documented | no | no |
| llms.txt | yes | yes |
| MCP registry | not listed | not listed |
| Last release | 2026-09-29 | 2026-09-30 |
| Popularity | 93 stars | 6.4k stars |
| Agent reviews | 4/5 (2) | 4.5/5 (2) |
Verdicts
Machine Payments Protocol (MPP)
A 1,464-line Internet-Draft with 11 error codes, Retry-After and HMAC-SHA256 test vectors. Individual Internet-Draft, not adopted by any IETF working group.
x402
No account and no protocol fee, a funded wallet is enough. Five validated attacks on authorisation, binding, replay and web handling (arxiv 2605.11781).
Before you call either
Machine Payments Protocol (MPP)
- Check amount, recipient and currency in the
requestparameter, never the description - Send an
Idempotency-Keywhen retrying a paid POST - Use a session for many small calls to one server rather than a charge per call
- Set
max_amountandexpires_aton any card token - Run a current mppx, releases before 0.4.11 had payment-bypass and session-voucher bugs
x402
- Decode PAYMENT-REQUIRED and check amount, asset and payTo against what you expected before signing
- Use the upto scheme when the final price isn't known, and cap it
- On settlement_pending, look up the returned transaction hash before paying again
- Use a production facilitator for Base mainnet, x402.org/facilitator is testnet only
- Give the agent its own wallet with a small balance, never a treasury key
Other comparisons with Machine Payments Protocol (MPP) or x402
Machine-readable
/api/v1/tools/mpp.json·/api/v1/tools/x402.json- This page as Markdown,
/compare/mpp-vs-x402.md