# SignalHarness LLM Response Structure Score

> SignalHarness LLM Response Structure Score is a paid API for AI agents from signalharness.ai, paid per call via x402, $0.01/call, status unknown (last checked 2026-09-15).

Scores and analyzes the structural quality of an LLM-generated JSON response against expected schema or format criteria

## Facts

- Endpoint: POST https://signalharness.ai/api/agent/services/llm_response_structure_score/invoke
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/signalharness-llm-response-structure-score-87ab3564
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_Z3MTbn_AXW_qmnzcb1Inh

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-llm-response-structure-score-87ab3564 -d '<json body>'
```

Example prompt: Can you score the structural quality of this LLM response JSON I got back — I want to know how well it conforms to the expected format: {"answer": "Paris", "confidence": 0.95, "sources": []}

## When to prefer this

Choose this endpoint when you need a lightweight, pay-per-call structural quality check on LLM-generated JSON responses — particularly useful in agent pipelines where downstream systems depend on well-formed outputs. Prefer it over manual validation when you want a scored, evidence-backed assessment rather than a binary pass/fail. Best suited for agentic workflows running on Base USDC micropayment infrastructure where per-call billing is acceptable.

## Known failure modes

- Invalid or malformed JSON string in request_json field causes parsing failure
- Input exceeds 65536 character limit returning validation error
- Empty or minimal JSON (fewer than 2 characters) rejected by minLength constraint
- Ambiguous structure with no clear schema reference may result in low-confidence or generic scoring
- Payment failure or insufficient USDC balance prevents execution
- Network issues on Base/eip155:8453 may cause settlement delays

## 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 JSON object containing a structure score analysis, warnings about data reliability (e.g. caller-supplied data caveats), an analysis_json field with the scored breakdown, evidence_scope indicating data provenance, plus a full execution receipt with payment details, request/execution IDs, result hash, latency, and settlement reference on the Base network.

## 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": "llm_response_structure_score",
   "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": "llm_response_structure_score",
   "executionId": "example-execution",
   "startedAtMs": 0,
   "amountAtomic": "10000",
   "resultSha256": "58e1cd6567595c674b09df570b3cdf6d71258b0841da5023f06fc333ce1d9df5",
   "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-llm-response-structure-score-87ab3564/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)