# SignalHarness Model Output Compare

> SignalHarness Model Output Compare is a paid API for AI agents from signalharness.ai, paid per call via x402, $0.015/call, status unknown (last checked 2026-09-13).

Compares and analyzes caller-supplied model outputs, returning structured analysis and validation results for AI-generated content.

## Facts

- Endpoint: POST https://signalharness.ai/api/agent/services/model_output_compare/invoke
- Price: $0.015/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-13
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/signalharness-model-output-compare-254c401c
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_yE1LsDOvubrudomYfwZ1k

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability signalharness-model-output-compare-254c401c -d '<json body>'
```

Example prompt: I have outputs from two different AI models for the same prompt — can you compare them and tell me which one is more accurate or consistent? Here's the JSON with both responses.

## When to prefer this

Choose this endpoint when you need a pay-per-call, agent-native comparison or validation of AI model outputs without standing up your own evaluation infrastructure. It is well-suited for lightweight, on-demand quality checks between model responses, especially in agentic pipelines that already use x402/Base USDC micropayments. Prefer alternatives if you need human-in-the-loop evaluation, large-scale batch benchmarking, or domain-specific scoring rubrics not supported by this service.

## Known failure modes

- Malformed or invalid JSON in request_json causes validation failure
- Caller-supplied data that cannot be parsed may return incomplete analysis
- Result warnings may indicate low confidence due to caller-supplied data scope
- Network or payment settlement failures may result in no receipt being issued
- Empty or too-short request_json (below minLength of 2) will be rejected

## How this service works

Explore 330 pay-per-call x402 API services and 27 agent-native digital products, with Base USDC pricing, secure Polar checkout, and free discovery.

## Output

Returns a structured JSON analysis of the submitted model output(s), including an analysis_json field with findings, a list of warnings (e.g. to verify caller-supplied data), an evidence_scope field indicating data provenance, a status field indicating success or failure, and a full payment receipt with execution metadata, latency, and a SHA-256 hash of the result.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "request_json": {
   "type": "string",
   "maxLength": 65536,
   "minLength": 2
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "replay": false,
  "result": {
   "warnings": [
    "Verify the caller-supplied data before relying on this result."
   ],
   "service_id": "model_output_compare",
   "analysis_json": "{\"example\":\"schema-valid caller-supplied data\"}",
   "evidence_scope": "caller_supplied_data"
  },
  "status": "succeeded",
  "receipt": {
   "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
   "usage": [],
   "status": "succeeded",
   "network": "eip155:8453",
   "artifacts": [],
   "endedAtMs": 0,
   "latencyMs": 0,
   "paymentId": "example-payment",
   "receiptId": "example-receipt",
   "requestId": "example-request",
   "serviceId": "model_output_compare",
   "executionId": "example-execution",
   "startedAtMs": 0,
   "amountAtomic": "15000",
   "resultSha256": "73660f33a70cec7e6e7fe190425c34f9cb9956f70616e7511b422ea6154fca27",
   "serviceVersion": "1.0.0",
   "settlementReference": "0x0000000000000000000000000000000000000000000000000000000000000000"
  },
  "artifacts": [],
  "requestId": "example-request",
  "executionId": "example-execution"
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/signalharness-model-output-compare-254c401c/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from signalharness.ai](https://www.zero.xyz/host/signalharness.ai/llms.txt)