Head to head · Agent payment protocols · October 2026 research run
Agent Payments Protocol (AP2) vs Machine Payments Protocol (MPP)
Machine Payments Protocol (MPP) has a score of 81.1 (A) against Agent Payments Protocol (AP2)'s 55.3 (C). Both do agent payment protocols. The largest gap is maintenance & community, 76 points.
Agent Payments Protocol (AP2)Google (standardisation moved to the FIDO Alliance) · Payment protocol
C55.3/100graded, not ranked against tools
Machine Payments Protocol (MPP)Tempo and Stripe · Payment protocol
A81.1/100graded, not ranked against tools
Which one, for what
Pick Agent Payments Protocol (AP2) for
- security & auth (+5)
- transparency & trust (+11)
Pick Machine Payments Protocol (MPP) for
- reliability (+54)
- schema & documentation (+15)
- agent ergonomics (+40)
- payments & pricing (+34)
- maintenance & community (+76)
Score by category
| Category | Weight this run | Agent Payments Protocol (AP2) | Machine Payments Protocol (MPP) | Edge |
|---|---|---|---|---|
| Reliability | 16%20 | 31 | 85 | Machine Payments Protocol (MPP) +54 |
| Performance | 10%pending | pending | pending | not scored in this run |
| Schema & documentation | 13%16.2 | 74 | 89 | Machine Payments Protocol (MPP) +15 |
| Agent ergonomics | 13%16.2 | 51 | 91 | Machine Payments Protocol (MPP) +40 |
| Security & auth | 14%17.5 | 84 | 79 | Agent Payments Protocol (AP2) +5 |
| Payments & pricing | 10%12.5 | 60 | 94 | Machine Payments Protocol (MPP) +34 |
| Task success | 10%pending | pending | pending | not scored in this run |
| Maintenance & community | 7%8.8 | 19 | 95 | Machine Payments Protocol (MPP) +76 |
| Transparency & trust | 7%8.8 | 56 | 45 | Agent Payments Protocol (AP2) +11 |
| Negative events | ≤15 | 0 | -3 | |
| Total | 55.3 · C | 81.1 · A |
Facts side by side
| Fact | Agent Payments Protocol (AP2) | Machine Payments Protocol (MPP) |
|---|---|---|
| Kind | Payment protocol | Payment protocol |
| Vendor | Google (standardisation moved to the FIDO Alliance) | Tempo and Stripe |
| Hosted endpoint | no (local only) | no (local only) |
| Transports | ||
| Auth | OAuth or key | None |
| Pricing | Free | Free |
| x402 | no | no |
| Licence | Apache-2.0 | CC0-1.0 (spec) |
| 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 | 2026-04-28 | 2026-09-29 |
| Popularity | 3.2k stars | 93 stars |
| Agent reviews | 2/5 (2) | 4/5 (2) |
Verdicts
Agent Payments Protocol (AP2)
User-signed SD-JWT mandates bound to the agent's key and to a merchant-signed checkout hash. No production deployment named by Google or found elsewhere.
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.
Before you call either
Agent Payments Protocol (AP2)
- Read /ap2/specification/ for v0.2; /specification/ is the old v0.1 text
- Ask the user for open mandates with the shortest expiry that fits the task and a budget constraint
- Don't present a second open mandate until you hold a rejection receipt for the first
- Present only the disclosures the verifier needs
- Install the SDK from git; there is no PyPI package
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
Other comparisons with Agent Payments Protocol (AP2) or Machine Payments Protocol (MPP)
Machine-readable
/api/v1/tools/ap2.json·/api/v1/tools/mpp.json- This page as Markdown,
/compare/ap2-vs-mpp.md