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Assurance Attest
x402
Assurance Attest is a paid API for AI agents from hermesplant.com, paid per call via x402, $0.05/call, status unknown (last checked 2026-09-15).
Creates a signed, machine-readable attestation record for consequential agent actions (x402 payments, MCP tool calls) with policy verdict and tamper-evident integrity proof.
Price / call$0.05
Success—
StatusUnknown
How this service works
Signed receipt for one agent action. Post an x402 payment intent or MCP tool call (optional policy + settlement outcome) and get a canonical HMAC-signed record: binding hash, verdict, findings, and a free public verify URL third parties can check without trusting your agent's logs. Loop it after every payment or tool call to build a tamper-evident audit trail. Canonicalization hermes-stable-json-v1; org history and probes available on Assurance plans.
Output
Returns a JSON object containing: an attestationId (att_<uuid>), a verdict (allow/deny), bindingHash, attestedAt timestamp, protocol, and optionally the settlement outcome. The integrity block includes an HMAC-SHA-256 signature, recordHash, keyId, and canonicalization method so the record can be independently verified via the /verify endpoint.
Example use cases
Audit trail for agent x402 payment
“My agent just processed an x402 payment to https://vendor.com/api/report — run ID is run-7f2a, agent ID is agent-finance-01, purpose is 'purchase analytics report'. Create a signed attestation for this with the settlement ID 0xabc999 and mark the outcome as fulfilled so I have a verifiable receipt.”
Safety gate log for MCP tool execution
“Before my agent calls the 'run_shell' tool on MCP server prod-infra-01 for run ID run-deploy-882, I need an attestation record that captures the tool name, arguments hash, and a policy verdict — use the mcp protocol and subject it to our default policy so we have an audit trail.”
Evidence record for rejected infrastructure action
“My agent tried to execute a database migration but it was rejected by policy during run run-sql-441, agent ID agent-db-ops, purpose 'schema migration'. Attest this with outcome rejected and protocol x402 so compliance has a machine-readable record of the blocked action.”
Technical details
Endpoint
GEThttps://hermesplant.com/api/agent-services/assurance/attestWhen to prefer
Use this endpoint when you need a cryptographically signed, machine-readable audit record for a specific consequential agent action — particularly x402 micropayments or MCP tool invocations — and require tamper-evident evidence suitable for compliance review or downstream verification. Prefer this over generic logging when policy verdict (allow/deny), HMAC integrity proofs, and a verifiable receipt with a settlementId are required. Choose the Quick Gate sibling if you only need a pre-action safety check without creating a persistent attestation record.
Side effects
- Missing required fields (runId, protocol, intent) returns a 400 validation error
- Invalid protocol value (not 'x402' or 'mcp') causes schema rejection
- Malformed intent object missing required subfields (resourceUrl for x402, serverId+toolName for mcp) returns an error
- Payment failure or USDC balance insufficient results in x402 payment required response
- Signature verification failure on the returned record indicates a server-side integrity issue
- Duplicate runId attestations may be rejected or flagged depending on policy configuration
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| intent | object | x402: resourceUrl+method (+scheme/network/asset/amountUnits/payTo). mcp: serverId+toolName (+toolArguments or toolArgumentsHash). |
| policy | object | Optional buyer policy (policyId+version, caps, allow-lists). Omit for a binding-only attestation under the permissive policy. |
| outcome | object | Optional settlement outcome: outcome fulfilled|failed|rejected, settlementId, responseStatus, evidenceHashes[]. |
| subject | object | Who acted: runId (required), agentId, purpose. |
| protocol | string | "x402" or "mcp". |
Output
Schema · Response
{
"type": "json",
"example": {
"record": {
"kind": "agent-action-attestation",
"outcome": {
"outcome": "fulfilled",
"settlementId": "0xsettle"
},
"verdict": "allow",
"protocol": "x402",
"attestedAt": "2026-07-12T00:00:00.000Z",
"bindingHash": "<sha256>",
"attestationId": "att_<uuid>"
},
"status": "attested",
"verify": {
"url": "https://hermesplant.com/api/agent-services/assurance/verify",
"method": "POST"
},
"service": "assurance",
"integrity": {
"keyId": "assurance-primary",
"signature": "<hmac>",
"recordHash": "<sha256>",
"canonicalization": "hermes-stable-json-v1",
"signatureAlgorithm": "HMAC-SHA-256"
}
}
}Tags
x402
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