MCA — Machine Commerce Attestation
The open evidence standard for the agent economy — who paid, under whose authority, what was delivered, and proof the record was never rewritten.
The stack
Where MCA sits
AI AGENTS
act, spend, and promise on your behalf
PAYMENT RAILS
x402 · AP2 · cards · ACH
MCA — THE EVIDENCE LAYER
signed, append-only attestation log
GOVERNANCE · RISK · DISPUTES
consume evidence, resolve trust
Rails prove money moved. MCA proves VALUE moved — and who authorized it.
The primitive
The commerce triple
REQUEST
hash: 9f2a…c1
PAYMENT
hash: 41bd…7e
DELIVERY
hash: e083…2f
Hashes and metadata only — payload bodies are prohibited by the spec.
Not a blockchain
Different layers, different jobs
Public blockchain
Witnesses its own transactions — blind to everything off-chain.
Smart contract
Executes on-chain logic — cannot attest real-world delivery.
Audit log
An internal record — mutable, and not independently verifiable.
MCA
A verifiable evidence layer across any rail, agent, or stack.
A chain can only witness the chain — MCA sees them all.
Composable: a blockchain makes an excellent witness for MCA checkpoints.
Don't trust — verify
Verify it yourself
# reference-verifier preview: 10/10; run to reproduce
# public descriptor only — not a log health check
The first command runs the upstream reference-verifier suite. The second fetches a descriptor only; descriptor availability is not verification of log health.
By the numbers
Small surface, hard guarantees
- independent implementations
- /9
- vendored reference-vector checks passing
- ≤ hr
- disclosed exposure window
- $
- to verify, forever
The 9/9 result is from repository checks against vendored mca-verify reference vectors, not a live-log health indicator. A missing latest checkpoint or empty root provides no checkpointed-record integrity evidence.