sm-arp — Agency Receipt Protocol

The portable, cryptographically signed receipt format AI agents emit when they act on behalf of humans. Runtime-agnostic, vendor-neutral, MIT-licensed.

ARP sits above MCP (tool integration) and A2A (agent-to-agent transport) — the human ↔ agent accountability layer those standards deliberately do not address.

Status

• WHITEPAPER.md — motivation, design choices, and how ARP fits the portfolio.
• spec/arp/0.1/spec.md — the canonical normative document (RFC-style).
• THREATMODEL.md — what a receipt does and does not prove, threats A1–A10, the delegation/transparency trust-rung roadmap, and a verifier checklist.

Use it as a library

ARP ships one canonical Python implementation, sm_arp, so every runtime imports the same build/sign/verify/store code instead of vendoring its own — the receipt envelope cannot drift between them. The library needs nothing but cryptography, base58, and jcs.

from sm_arp import Identity, build_action, issue_receipt, verify_receipt, IssuerLog

me = Identity.generate()
r = issue_receipt(me, principal_did=me.did,
                  action=build_action(category="data_shared", human_summary="shared my calendar"))
assert verify_receipt(r).ok                 # structure → signature → authority → hash chain
IssuerLog("log.sqlite").append(r)           # SQLite Issuer/Agency Log, hash-chained per issuer

sm_arp's verifier is tested against the canonical 22-vector corpus and asserted byte-for-byte equal to the conformance harness's verdict on every vector — so the library and the spec cannot disagree.

Layout

• sm_arp/ — the consumable library: identity (Ed25519 + did:key), receipts (build/sign/verify/canonical/chain), store (SQLite Issuer/Agency Log).
• arp_cli/ — the arp command-line tool (pip install 'sm-arp[cli]').
• WHITEPAPER.md — design rationale and portfolio positioning.
• spec/arp/0.1/spec.md — the canonical normative receipt spec (RFC-style).
• spec/arp/0.1/conformance.md — ARP conformance criteria; points at sm-conformance for the badge.
• spec/arp/0.1/governance.md — stewardship and the path to public publication.
• spec/arp/0.1/dat-companion.md — the Delegated Authority Token sketch the authority chain references.
• schema/arp/0.1/ — JSON Schemas (Draft 2020-12) for the receipt envelope.
• vectors/arp/0.1/ — 22 language-agnostic receipt vectors.
• conformance/arp/ — framework-agnostic Python conformance harness for receipts.

The conformance badge lives in sm-conformance

ARP owns what a conformant runtime must do (this repo) and the receipt vectors it is tested against. It does not own the signed-badge mechanism — that is a generic, protocol-neutral substrate that lives in its own primitive, sm-conformance. ARP is its first consumer.

How to claim ARP compliance

1. Implement the spec in your runtime.
2. Run pytest conformance/ against the bundled vectors. Every positive vector MUST pass; every negative vector MUST be rejected at the documented stage.
3. Produce a signed conformance badge with sm-conformance and ship it at your runtime's .nanda/conformance.json — and, if you serve it over HTTP, at the canonical /.well-known/conformance.json (see sm-conformance SPEC §3.2).

The badge is self-signed and independently re-verifiable: anyone can recompute pytest conformance/ against the bundled vectors and check the signature offline.

Implementing ARP

ARP is runtime-agnostic — any agent stack can emit conformant receipts. Implement the spec, pass conformance/, and ship a signed sm-conformance badge. The receipt format depends on nothing but Ed25519, JCS, and the W3C did:key method.

License

MIT — see LICENSE.