# 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. Category scores, facts, verdicts and agent notes side by side.

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- Updated: 2026-10-05

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): grade A, 81.1/100, rank graded, not ranked against tools. Markdown https://www.anchorterminal.com/tools/mpp.md · JSON https://www.anchorterminal.com/api/v1/tools/mpp.json
- x402: grade A, 79.7/100, rank graded, not ranked against tools. Markdown https://www.anchorterminal.com/tools/x402.md · JSON https://www.anchorterminal.com/api/v1/tools/x402.json

## 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 | Machine Payments Protocol (MPP) | x402 | Edge |
| --- | --- | --- | --- | --- |
| Reliability | 16% (20 this run) | 85 | 87 | x402 +2 |
| Performance | 10%, pending | pending | pending | not scored in this run |
| Schema & documentation | 13% (16.2 this run) | 89 | 86 | Machine Payments Protocol (MPP) +3 |
| Agent ergonomics | 13% (16.2 this run) | 91 | 84 | Machine Payments Protocol (MPP) +7 |
| Security & auth | 14% (17.5 this run) | 79 | 67 | Machine Payments Protocol (MPP) +12 |
| Payments & pricing | 10% (12.5 this run) | 94 | 97 | x402 +3 |
| Task success | 10%, pending | pending | pending | not scored in this run |
| Maintenance & community | 7% (8.8 this run) | 95 | 93 | Machine Payments Protocol (MPP) +2 |
| Transparency & trust | 7% (8.8 this run) | 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)

1. Check amount, recipient and currency in the `request` parameter, never the description
2. Send an `Idempotency-Key` when retrying a paid POST
3. Use a session for many small calls to one server rather than a charge per call
4. Set `max_amount` and `expires_at` on any card token
5. Run a current mppx, releases before 0.4.11 had payment-bypass and session-voucher bugs

### x402

1. Decode PAYMENT-REQUIRED and check amount, asset and payTo against what you expected before signing
2. Use the upto scheme when the final price isn't known, and cap it
3. On settlement_pending, look up the returned transaction hash before paying again
4. Use a production facilitator for Base mainnet, x402.org/facilitator is testnet only
5. Give the agent its own wallet with a small balance, never a treasury key

## Other comparisons with Machine Payments Protocol (MPP) or x402

- [Agentic Commerce Protocol (ACP) vs Machine Payments Protocol (MPP)](https://www.anchorterminal.com/compare/acp-vs-mpp.md)
- [Agentic Commerce Protocol (ACP) vs x402](https://www.anchorterminal.com/compare/acp-vs-x402.md)
- [Agent Payments Protocol (AP2) vs Machine Payments Protocol (MPP)](https://www.anchorterminal.com/compare/ap2-vs-mpp.md)
- [Agent Payments Protocol (AP2) vs x402](https://www.anchorterminal.com/compare/ap2-vs-x402.md)
- [L402 vs Machine Payments Protocol (MPP)](https://www.anchorterminal.com/compare/l402-vs-mpp.md)
- [L402 vs x402](https://www.anchorterminal.com/compare/l402-vs-x402.md)