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Penny Engine — AI Agent Outcome Guard
x402
Penny Engine — AI Agent Outcome Guard is a paid API for AI agents from penny-paid-batch-production.up.railway.app, paid per call via x402, $0.001/call, status unknown (last checked 2026-10-19).
Validates AI agent output against declared expectations, returning a deterministic PASS/FAIL verdict and SHA-256 fingerprint of the result.
Price / call$0.001
Success—
StatusUnknown
How this service works
Machine-to-machine result validation via x402. One structured call, deterministic PASS or FAIL and SHA-256 fingerprint, $0.001 USDC on Base.
Output
Returns a JSON object with a boolean 'passed' field, a 'verdict' string ('PASS' or 'FAIL'), an 'evidence' object containing the hashing algorithm name ('SHA-256') and the SHA-256 hash of the submitted result, and a 'checksTotal' integer indicating how many validation checks were evaluated.
Example use cases
Guard a research agent's summary output
“My research agent just returned a result — validate that it has a non-empty 'findings' field, that 'confidence' is between 0.75 and 1.0, and that 'status' equals 'done'. I need a PASS or FAIL before I hand this off to the next step.”
Audit a pricing agent before executing a trade
“Before I act on this pricing agent output, check that 'price' is between 99.5 and 102.0, 'ticker' equals 'AAPL', and 'timestamp' is non-empty. Return the verdict and the SHA-256 fingerprint so I can log it.”
Validate customer-facing AI response quality
“I have an AI-generated customer reply — verify that 'tone' equals 'professional', the 'body' path is non-empty, and 'wordCount' is between 50 and 300. Tell me if it passes and give me the result hash.”
Technical details
Endpoint
POSThttps://penny-paid-batch-production.up.railway.app/api/proof-gate?utm_source=zero.xyzWhen to prefer
Choose this endpoint when you need a lightweight, pay-per-call, cryptographically auditable quality gate for structured AI agent outputs — especially in automated M2M pipelines where you need a tamper-evident fingerprint alongside a binary verdict. It is ideal when you want deterministic validation rules (field existence, value equality, numeric ranges) rather than semantic or LLM-based evaluation. At $0.001 USDC per call it is cost-effective for high-frequency agent monitoring.
Side effects
- Missing or malformed 'result' object causes validation to fail with an error response
- Empty or invalid 'expectations' object may result in zero checks and an ambiguous outcome
- Payment failure via x402 returns HTTP 402 and no validation is performed
- Malformed JSON in the request body returns an HTTP 400 error
- Network timeout or Railway infrastructure unavailability returns HTTP 5xx
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| result | object | |
| expectations | object |
Output
Schema · Response
{
"type": "json",
"example": {
"passed": true,
"service": "M2M Agent Outcome Guard",
"verdict": "PASS",
"evidence": {
"algorithm": "SHA-256",
"resultSha256": "example_only"
},
"checksTotal": 4
}
}Tags
x402
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