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SettlementWitness

Remote-first MCP adapter for emitting Settlement Attestation Receipts; not a verifier.

Links

Repository

README

From the repo.

DefaultVerifier — SAR Verification Infrastructure

SAR (Settlement Attestation Receipt) is a verification protocol that produces cryptographically signed receipts proving whether an AI agent completed a task according to its specification.

DefaultVerifier is a live SAR verifier implementation with a public receipt registry, metrics API, and explorer.

If it matters—Verify it.

Architecture

Understand the SAR stack and verification model:

👉 SAR Architecture

Example Response

{ "witness": "SettlementWitness", "witness_version": "v0", "task_id": "example", "verifier_endpoint": "https://defaultverifier.com/verify", "witness_timestamp": "2026-01-01T00:00:00Z", "receipt_id": "...", "receipt": { "profile": "settlement-witness-verified-v0.2", "task_id_hash": "sha256:...", "verdict": "PASS", "reason_code": "CONDITION_SATISFIED", "ts": "...", "verifier_kid": "...", "counterparty": "0xABC...", "receipt_id": "sha256:...", "sig": "base64url:..." },

"_ext": { "agent_id": "0x123:demo" } }

Notes

  • the receipt payload is issued under the settlement-witness-verified-v0.2 profile; verdicts are PASS, FAIL, or INDETERMINATE
  • when counterparty is present, it is included in signature scope and in receipt_id derivation
  • retired signer keys remain valid for verifying receipts they historically signed; verifier_kid in a receipt is historical evidence and is never rewritten
  • current signer lifecycle (which kid is active vs. retired) is published at https://defaultverifier.com/.well-known/sar-keys.json — treat that endpoint, not this README, as the source of truth for which key is currently active
  • this behavior is implemented and publicly verifiable via the live receipt and key endpoints

SAR Compatibility: This implementation follows SAR verification semantics, with an extended signed payload when counterparty is present.

Demo

Run a full end-to-end verification in ~2 minutes: DEMO.md

Quick Start

1. Create a receipt

curl -X POST https://defaultverifier.com/settlement-witness
-H 'content-type: application/json'
-d '{ "task_id":"quickstart-001", "spec":{"checks":[{"kind":"field_equals","inputs":{"output_path":"$.result"},"expected":"hello"}]}, "output":{"result":"hello"}, "counterparty":"0x1234567890abcdef1234567890abcdef12345678" }'

2. Fetch the receipt

curl https://defaultverifier.com/settlement-witness/receipt/<receipt_id>

Note: use the receipt_id from the returned receipt

3. Verify locally (Node)

cd examples/node-verify node verify.js receipt.json jwks.json

Examples

Node.js verification example: examples/node-verify/

Python verification example: examples/verify_receipt_python.py

Usage: python3 examples/verify_receipt_python.py <receipt_id>

API Endpoints

Create Receipt

POST /settlement-witness

Submits a task verification request and returns a signed SAR receipt.

Retrieve Receipt

GET /settlement-witness/receipt/{receipt_id}

Note: Use the receipt_id from the returned receipt (sha256:...) for retrieval.

Returns a previously issued receipt.

Wallet Receipt Explorer

GET /settlement-witness/receipts?wallet={address}

Returns recent receipts associated with a wallet address.

The public explorer is available at:

https://defaultverifier.com/explorer

This interface allows browsing recent receipts and wallet-indexed delivery history.

Public Verification Keys

https://defaultverifier.com/.well-known/jwks.json

Alternative (SAR protocol reference): https://defaultverifier.com/.well-known/sar-keys.json

Used to verify Ed25519 signatures for receipts.

Key Registry

https://defaultverifier.com/.well-known/sar-keys.json

Registry of verifier public keys referenced by verifier_kid.

Config for your environment

Use the endpoint URL below in your config. No API key — you connect directly.

Tool

OS

Config file: ~/.cursor/mcp.json

{
  "mcpServers": {
    "mcp-server": {
      "url": "https://defaultverifier.com/mcp"
    }
  }
}

Paste into mcpServers in the config file. Restart Cursor after saving.

If this MCP is also published on mcpchannel.ai, you can subscribe from Browse and use the gateway config there instead.