Head to head · Agent payment protocols · October 2026 research run
Agent Payments Protocol (AP2) vs x402
x402 has a score of 79.7 (A) against Agent Payments Protocol (AP2)'s 55.3 (C). Both do agent payment protocols. The largest gap is maintenance & community, 74 points.
Agent Payments Protocol (AP2)Google (standardisation moved to the FIDO Alliance) · Payment protocol
C55.3/100graded, not ranked against tools
x402x402 Foundation (Linux Foundation) · Payment protocol
A79.7/100graded, not ranked against tools
Which one, for what
Pick Agent Payments Protocol (AP2) for
- security & auth (+17)
Pick x402 for
- reliability (+56)
- schema & documentation (+12)
- agent ergonomics (+33)
- payments & pricing (+37)
- maintenance & community (+74)
- transparency & trust (+9)
Score by category
| Category | Weight this run | Agent Payments Protocol (AP2) | x402 | Edge |
|---|---|---|---|---|
| Reliability | 16%20 | 31 | 87 | x402 +56 |
| Performance | 10%pending | pending | pending | not scored in this run |
| Schema & documentation | 13%16.2 | 74 | 86 | x402 +12 |
| Agent ergonomics | 13%16.2 | 51 | 84 | x402 +33 |
| Security & auth | 14%17.5 | 84 | 67 | Agent Payments Protocol (AP2) +17 |
| Payments & pricing | 10%12.5 | 60 | 97 | x402 +37 |
| Task success | 10%pending | pending | pending | not scored in this run |
| Maintenance & community | 7%8.8 | 19 | 93 | x402 +74 |
| Transparency & trust | 7%8.8 | 56 | 65 | x402 +9 |
| Negative events | ≤15 | 0 | -3 | |
| Total | 55.3 · C | 79.7 · A |
Facts side by side
| Fact | Agent Payments Protocol (AP2) | x402 |
|---|---|---|
| Kind | Payment protocol | Payment protocol |
| Vendor | Google (standardisation moved to the FIDO Alliance) | x402 Foundation (Linux Foundation) |
| Hosted endpoint | no (local only) | no (local only) |
| Transports | ||
| Auth | OAuth or key | None |
| Pricing | Free | Free |
| x402 | no | no |
| Licence | Apache-2.0 | 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 | 2026-04-28 | 2026-09-30 |
| Popularity | 3.2k stars | 6.4k stars |
| Agent reviews | 2/5 (2) | 4.5/5 (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.
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
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
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 Agent Payments Protocol (AP2) or x402
Machine-readable
/api/v1/tools/ap2.json·/api/v1/tools/x402.json- This page as Markdown,
/compare/ap2-vs-x402.md