Evidence Verification API

$0.05/call

Verify the evidence bundle before trusting a paid agent result.

POST /api/agent-services/evidence/verify

x402evidenceverificationagent-commerceaudit

What it does

Verify an agent-commerce evidence bundle before trusting a paid result. Evaluates shared evidence artifacts for x402 challenge presence, optional receipt, policy decision, final service response, endpoint and method binding, network, payTo, price, artifact source, freshness, hashes, and synthetic-proof leakage. Returns verified / needs_review / rejected / insufficient_evidence with per-rule evidence and the exact record an agent should persist with its run log.

Checks x402 challenge, policy decision, receipt, and service response artifacts
Rejects endpoint, method, network, payTo, and price mismatches
Returns a run-log policy record with per-rule evidence

Example request

POST /api/agent-services/evidence/verify

{
  "subject": {
    "kind": "agent_service_call",
    "serviceId": "payment-policy-decide",
    "endpoint": "/api/agent-services/payment-policy/decide",
    "method": "POST",
    "runId": "agent-run-2026-06-24-001"
  },
  "artifacts": [
    {
      "type": "x402_challenge",
      "source": "https://hermesplant.com/.well-known/x402",
      "collectedAt": "2026-06-24T12:00:00.000Z",
      "serviceId": "payment-policy-decide",
      "endpoint": "/api/agent-services/payment-policy/decide",
      "method": "POST",
      "network": "eip155:8453",
      "payTo": "0x6d6E695b09861467c7d462f5AAF31cF3540B9192",
      "priceCents": 5,
      "hash": {
        "algorithm": "sha256",
        "value": "<challenge-sha256>"
      }
    },
    {
      "type": "payment_policy_decision",
      "source": "hermes-policy",
      "serviceId": "payment-policy-decide",
      "endpoint": "/api/agent-services/payment-policy/decide",
      "method": "POST",
      "decision": "allow",
      "hash": {
        "algorithm": "sha256",
        "value": "<policy-sha256>"
      }
    },
    {
      "type": "service_response",
      "source": "agent-run-log",
      "serviceId": "payment-policy-decide",
      "endpoint": "/api/agent-services/payment-policy/decide",
      "method": "POST",
      "status": 200,
      "hash": {
        "algorithm": "sha256",
        "value": "<response-sha256>"
      }
    }
  ],
  "policy": {
    "expectedServiceId": "payment-policy-decide",
    "expectedEndpoint": "/api/agent-services/payment-policy/decide",
    "expectedMethod": "POST",
    "expectedNetwork": "eip155:8453",
    "expectedPriceCents": 5,
    "requireX402Challenge": true,
    "requirePolicyDecision": true,
    "requireServiceResponse": true,
    "requireArtifactHashes": true
  }
}

Example response (HTTP 200)

Deterministic — the same inputs always return the same audited output.

{
  "status": "verified",
  "service": "evidence-verify",
  "requestId": "ev_<uuid>",
  "evidenceVersion": "evidence-contract-v1",
  "decision": "verified",
  "confidence": 0.94,
  "verified": true,
  "artifactSummary": {
    "total": 3,
    "byType": {
      "x402_challenge": 1,
      "payment_policy_decision": 1,
      "service_response": 1
    },
    "sources": [
      "agent-run-log",
      "hermes-policy",
      "https://hermesplant.com/.well-known/x402"
    ],
    "hashed": 3,
    "synthetic": 0
  },
  "requiredArtifacts": [
    "x402_challenge",
    "payment_policy_decision",
    "service_response"
  ],
  "missingArtifacts": [],
  "reasonCodes": [
    "evidence.verified"
  ],
  "findings": [
    {
      "rule": "evidence.verified",
      "severity": "info",
      "disposition": "verified",
      "why": "Required evidence artifacts are present and match policy.",
      "evidence": "artifacts=3",
      "fix": null
    }
  ],
  "recommendedAction": "persist_evidence_and_use_result"
}

Input schema

Top-level request fields. Nested shapes are shown in the example above and the OpenAPI spec.

Field	Type	Required	Description
subject	object	—	Optional run subject: kind, serviceId, endpoint, method, resourceUrl, runId.
artifacts	array	Yes	Evidence artifacts using the shared Hermes contract. Supported types include x402_challenge, x402_receipt, payment_policy_decision, service_response, openapi_operation, api_catalog_entry, mcp_tool_manifest, agent_run_log, human_approval, merchant_identity, entitlement, checkout_session, and other.
policy	object	—	Verification policy: expectedServiceId, expectedEndpoint, expectedMethod, expectedNetwork, expectedPayTo, expectedPriceCents, allowedSources, minArtifacts, maxArtifactAgeSeconds, allowSyntheticEvidence, requireX402Challenge, requireX402Receipt, requirePolicyDecision, requireServiceResponse, and requireArtifactHashes.

How to call it over x402

1. Send the request. The first unpaid call returns HTTP 402 with an x402 payment challenge — $0.05, USDC on Base, and the recipient.
2. Pay per call. Your x402 client signs the USDC payment and retries automatically — no API key, no account, no subscription. New to x402?
3. Read the result. HTTP 200 returns the computed values plus evidence-backed findings.

With the x402 fetch client (Node / TypeScript)

import { wrapFetchWithPayment } from "@x402/fetch";
import { privateKeyToAccount } from "viem/accounts";

const account = privateKeyToAccount(process.env.AGENT_WALLET_KEY);
const pay = wrapFetchWithPayment(fetch, account); // USDC on Base

const res = await pay("https://hermesplant.com/api/agent-services/evidence/verify", {
  method: "POST",
  headers: { "content-type": "application/json" },
  body: JSON.stringify({
  "subject": {
    "kind": "agent_service_call",
    "serviceId": "payment-policy-decide",
    "endpoint": "/api/agent-services/payment-policy/decide",
    "method": "POST",
    "runId": "agent-run-2026-06-24-001"
  },
  "artifacts": [
    {
      "type": "x402_challenge",
      "source": "https://hermesplant.com/.well-known/x402",
      "collectedAt": "2026-06-24T12:00:00.000Z",
      "serviceId": "payment-policy-decide",
      "endpoint": "/api/agent-services/payment-policy/decide",
      "method": "POST",
      "network": "eip155:8453",
      "payTo": "0x6d6E695b09861467c7d462f5AAF31cF3540B9192",
      "priceCents": 5,
      "hash": {
        "algorithm": "sha256",
        "value": "<challenge-sha256>"
      }
    },
    {
      "type": "payment_policy_decision",
      "source": "hermes-policy",
      "serviceId": "payment-policy-decide",
      "endpoint": "/api/agent-services/payment-policy/decide",
      "method": "POST",
      "decision": "allow",
      "hash": {
        "algorithm": "sha256",
        "value": "<policy-sha256>"
      }
    },
    {
      "type": "service_response",
      "source": "agent-run-log",
      "serviceId": "payment-policy-decide",
      "endpoint": "/api/agent-services/payment-policy/decide",
      "method": "POST",
      "status": 200,
      "hash": {
        "algorithm": "sha256",
        "value": "<response-sha256>"
      }
    }
  ],
  "policy": {
    "expectedServiceId": "payment-policy-decide",
    "expectedEndpoint": "/api/agent-services/payment-policy/decide",
    "expectedMethod": "POST",
    "expectedNetwork": "eip155:8453",
    "expectedPriceCents": 5,
    "requireX402Challenge": true,
    "requirePolicyDecision": true,
    "requireServiceResponse": true,
    "requireArtifactHashes": true
  }
}),
});

const result = await res.json();

Inspect the 402 with curl

curl -i -X POST https://hermesplant.com/api/agent-services/evidence/verify \
  -H "content-type: application/json" \
  -d '{"subject":{"kind":"agent_service_call","serviceId":"payment-policy-decide","endpoint":"/api/agent-services/payment-policy/decide","method":"POST","runId":"agent-run-2026-06-24-001"},"artifacts":[{"type":"x402_challenge","source":"https://hermesplant.com/.well-known/x402","collectedAt":"2026-06-24T12:00:00.000Z","serviceId":"payment-policy-decide","endpoint":"/api/agent-services/payment-policy/decide","method":"POST","network":"eip155:8453","payTo":"0x6d6E695b09861467c7d462f5AAF31cF3540B9192","priceCents":5,"hash":{"algorithm":"sha256","value":"<challenge-sha256>"}},{"type":"payment_policy_decision","source":"hermes-policy","serviceId":"payment-policy-decide","endpoint":"/api/agent-services/payment-policy/decide","method":"POST","decision":"allow","hash":{"algorithm":"sha256","value":"<policy-sha256>"}},{"type":"service_response","source":"agent-run-log","serviceId":"payment-policy-decide","endpoint":"/api/agent-services/payment-policy/decide","method":"POST","status":200,"hash":{"algorithm":"sha256","value":"<response-sha256>"}}],"policy":{"expectedServiceId":"payment-policy-decide","expectedEndpoint":"/api/agent-services/payment-policy/decide","expectedMethod":"POST","expectedNetwork":"eip155:8453","expectedPriceCents":5,"requireX402Challenge":true,"requirePolicyDecision":true,"requireServiceResponse":true,"requireArtifactHashes":true}}'
# → HTTP/1.1 402 Payment Required  (x402 challenge: price, USDC asset, Base network, recipient)
# → sign the USDC-on-Base payment and retry to receive HTTP 200

Prefer zero code? This endpoint is also exposed as a tool on the Hermes Plant MCP server, so an MCP-capable agent can call it with its own x402 wallet.