An open standard for tamper-evident attestation of machine commerce — who paid, under whose authority, what was delivered, and proof the record was never rewritten.
As AI agents become paying participants of the internet (x402-class rails, AP2, card-network agent protocols), the payment rails define how machines pay. MCA defines how anyone proves it afterward — a rail-agnostic attestation record format, append-only hash-chained logs, and RFC-6962-style Merkle checkpoints with independent witnessing. Certificate Transparency for machine commerce.
- Read the specification → (Draft v0.1, open for community review)
- Reference verifier:
mca-verify— dependency-free, Apache-2.0, with conformance vectors - Reference log: operated by IONDRA — live in public Ed25519 mode; first independently verifiable attested machine payment at iondra.com/proof/0
- Reference witness:
mca-witness-worker— an independent witness on Cloudflare Workers (addendum 0.1.1, Section 8) - Governance: GOVERNANCE.md — public PRs, 14-day comment windows, stated path to neutral stewardship
Every participant in the agent economy profits from more spending — the rails from volume, the sellers from consumption — except the organization whose agents do the buying. And a payment network attesting to its own transactions is a company auditing itself. The evidence layer must be neutral, open, and verifiable by anyone. That is MCA.
- Attestation Records — one immutable statement per event, JCS-canonicalized, SHA-256 hash-chained
- Checkpoints — Ed25519-signed Merkle commitments (RFC 6962) with independent witnessing
- The Commerce Triple — request hash + payment receipt + delivered-content hash: proof that value moved, not just money
- Privacy by construction — hashes and bounded metadata only; payload bodies are never logged
- Verification — four procedures any party can run without trusting the log operator
v0.1 public draft plus addendum 0.1.1 (Log Descriptor, witness entry and descriptor, key_id derivation, hash-only profile, served inclusion-proof form; see CHANGELOG). Feedback via issues. v0.2 targets: normative mandate profile, witness gossip, multi-log cross-anchoring.
Specification text CC-BY-4.0 · Reference code Apache-2.0 · Initiated by IONDRA