tersign

Tersign is the evidence layer for the agent economy — a neutral, counter-signed, hash-chained ledger for agent commerce. Sellers sign EIP-712 receipts; Tersign chains them per seller and counter-signs every entry. When the dispute comes, the transcript is already sealed.

Venues rotate. The transcript endures.

Verify a Real Entry — Right Now

No account. No API key. This is the genesis receipt, seq 1 on the production chain:

npx tersign verify 0xe5874f1ffe87f0a6dd9eb157730f67b86ee4538b125fe30fcc4e165213dd3fc4 --ledger https://tersign.ai

ledger: counter-signed OK (seller tersign-first, seq 1 …) VALID

npx tersign verify <receipt.json | 0xdigest> [--ledger url] recovers the EIP-712 signature locally, then checks the entry against the public chain — yours or anyone's. Prefer raw HTTP? The same proof, no CLI:

curl https://tersign.ai/v1/receipts/0xe5874f1ffe87f0a6dd9eb157730f67b86ee4538b125fe30fcc4e165213dd3fc4/verify

Chain of Custody

Every entry takes the same path: the seller signs the receipt (EIP-712, x402 offer-receipt extension) → Tersign computes the keccak256 canonical digest → the digest joins that seller's hash chain, each seq n bound to seq n−1 → the neutral ledger counter-signs (secp256k1) → anyone verifies, and any venue gets a serialized envelope.

graph LR
    A["agent transaction<br/>x402"] --> B["seller-signed receipt<br/>EIP-712"]
    B --> C["canonical digest<br/>keccak256"]
    C --> D["per-seller hash chain<br/>seq n binds seq n−1"]
    D --> E["neutral counter-signature<br/>secp256k1 ledger"]
    E --> F["verifiable by anyone<br/>venue-ready envelope"]

_{Diagram renders on GitHub. On npm, the paragraph above IS the diagram.}

Refunds chain back to the original receipt via refundOf. Disputes attach to the digest with objective reason codes. Party statements are structurally segregated behind an UNVERIFIED marker — the evidence stays prompt-injection-hardened.

Enter the Record

npm i tersign

withAssure() wraps your x402 fetch handler so every paid call issues a signed, chained receipt. The full register:

Capability	In the record
Receipts	Seller-signed EIP-712 (x402 offer-receipt extension), keccak256 canonical digests
withAssure()	x402 fetch-handler adapter — a receipt per paid call
Compliance records	EU Art-226b minimal tier · EN 16931 full tier · HK IRO s.51C retention
Action records	ActionRecordV1 — GDPR-minimized; captures the content of an Art-50 disclosure so the disclosure itself is independently attested, not self-reported
Refunds	Chained to the original receipt via refundOf
Disputes v0	Objective reason codes, evidence submission, adjudication
Venue envelopes	Internet Court (5,000-char slot) · Kleros ERC-1497 · UMA · generic
Evidence packs	format=art50 · format=safr (beta)
Idempotency	In-memory + Cloudflare D1 stores

For Agents — the MCP Server

npx tersign starts the MCP server (stdio). Official registry entry: io.github.tersignhq/evidence (active).

{
  "mcpServers": {
    "tersign": {
      "command": "npx",
      "args": ["tersign"],
      "env": { "TERSIGN_SELLER_KEY": "0x<your-seller-key>" }
    }
  }
}

Tools — issue_receipt · verify_receipt · verify_compliance_record · record_refund · open_dispute · submit_dispute_evidence · adjudicate_dispute · get_dispute

Env var	Required	Purpose
TERSIGN_SELLER_KEY	yes	0x-prefixed private key that signs your receipts and records
TERSIGN_LEDGER_URL	no	hosted ledger for counter-signing + chain checks
TERSIGN_LEDGER_API_KEY	no	your seller API key on that ledger
TERSIGN_LEDGER_SELLER_ID	no	your seller id on that ledger
TERSIGN_ISSUER_NAME	no	issuer name stamped on compliance records
TERSIGN_ISSUER_JURISDICTION	no	issuer jurisdiction stamped on compliance records

Cold to counter-signed in one session: call issue_receipt, then check the issued receipt's digest with npx tersign verify <digest> --ledger <url>.

The agent skill tersign-evidence ships at tersignhq/skills.

The Live Record

• Ledger + dashboard — public verify page: https://tersign.ai/verify
• Census — hash-chained observations across the live x402 seller catalog, probed autonomously; the numbers are served live, never quoted stale: https://prober.tersign.ai/v1/prober/stats
• Conformance — RFC 8785 (JCS) canonical serialization, keccak256 digests, and the public two-sided vector suite (independence, completeness, existence, phase): tersignhq/evidence-record-conformance. Reproduce the bytes and your implementation is conformant — in any language.
• Standards — the compliance-fields extension — a typed compliance-record schema plus three evaluator-side disqualifications (independence, completeness/existence, economic-phase separation), each executable as a two-sided conformance vector — is under review upstream (x402-foundation/x402#2853) and referenced in the x402 TSC's evidence-record charter agenda (tsc#4). The merged offer-receipt spec already carries the completeness criterion at SHOULD strength (§4.5.1, #2811).

Machine Surfaces

Full URLs, readable without auth. If you are an agent, start here.

Surface	Address
npm package	tersign — https://www.npmjs.com/package/tersign
MCP registry	io.github.tersignhq/evidence
ARD catalog (Agentic Resource Discovery)	https://tersign.ai/.well-known/ai-catalog.json
Verify API	GET https://tersign.ai/v1/receipts/{digest}/verify
Envelope API	GET https://tersign.ai/v1/receipts/{digest}/envelope?venue={internet-court|kleros|uma|generic}
Ledger stats	GET https://tersign.ai/v1/stats
Ledger signer	GET https://tersign.ai/v1/ledger
llms.txt	https://raw.githubusercontent.com/tersignhq/tersign-js/main/llms.txt
Conformance vectors (RFC 8785 + keccak256)	https://github.com/tersignhq/tersign-js/blob/main/test/fixtures/canonical-vectors.json
Sample compliance record + digests	https://github.com/tersignhq/tersign-js/blob/main/test/fixtures/compliance-record.json
Genesis verify	npx tersign verify 0xe5874f1ffe87f0a6dd9eb157730f67b86ee4538b125fe30fcc4e165213dd3fc4 --ledger https://tersign.ai

_{MIT · built and published from tersignhq/tersign-js via trusted-publishing CI, provenance attested · tersign reserved on PyPI}

_{Venues rotate. The transcript endures.}