Why a receipt layer, across all four protocols
The agentic-payments ecosystem is converging on four protocols: x402, AP2, A2A and MPP. They differ in how an agent is charged (per request, per mandate, per agent-call, per method) but share one unmet requirement: a portable, verifiable record of the compliance and settlement decision that outlives the session that produced it. A receipt layer is valuable only if it holds three properties:- Deterministic. The same logical decision serialises to the same bytes everywhere. AlgoVoi pins JCS, RFC 8785 as the canonical preimage form.
- Recomputable. Anyone can re-derive the hash from the retained bytes, with no dependence on an
out-of-band rule registry, via an in-band
canon_version. - Offline-verifiable and no PII. Verification needs no live call to AlgoVoi, and the receipt carries categorical outcomes, not customer data. See the compliance receipt format and receipt verifier.
One substrate, every protocol
| Protocol | What it charges for | AlgoVoi receipt |
|---|---|---|
| x402 | per HTTP request (HTTP 402) | compliance receipt at admission, settlement attestation on-chain |
| AP2 | per signed mandate | mandate-bound compliance receipt plus settlement attestation |
| A2A | per agent-to-agent task | payment-gated task receipt on the same substrate |
| MPP | per JSON-RPC method or MCP tool call | per-method compliance receipt |
action_ref primitive,
SHA-256( JCS( { agent_id, action_type, scope, timestamp_ms } ) ), binds the agent, the action, and
the settlement into one recomputable anchor regardless of which protocol carried the payment.
How a receipt is proven
- The gateway screens the incoming request (sanctions / PEP / AML, bring-your-own provider) and emits a categorical ALLOW / REFER / DENY compliance receipt.
- The receipt is canonicalised under JCS RFC 8785 and signed (RFC 9421, with a post-quantum option via the PQC substrate).
- On settlement, a settlement attestation chains the on-chain
transaction to the same
action_ref. - Any party recomputes the canonical bytes and verifies the signature offline, at any later date, with the open receipt verifier.
Standards backing
The substrate is specified in AlgoVoi-authored IETF Internet-Drafts and cross-validated byte for byte across eight independent JCS implementations in eight languages:draft-hopley-x402-canonicalisation-jcs-v1: the canonicalisation discipline.draft-hopley-x402-compliance-receipt: the compliance receipt format.
Next
- Start with the JCS canonicalisation substrate.
- See the per-protocol pages: x402, AP2, A2A, MPP.
- Verify a receipt yourself with the open receipt verifier.