# SignalHarness Prompt Output Contract Extractor

> SignalHarness Prompt Output Contract Extractor is a paid API for AI agents from signalharness.ai, paid per call via x402, $0.005/call, status unknown (last checked 2026-09-15).

Extracts structured output contracts (schemas, constraints, and response formats) from prompt/request JSON submitted by the caller

## Facts

- Endpoint: POST https://signalharness.ai/api/agent/services/prompt_output_contract_extract/invoke
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/signalharness-prompt-output-contract-extractor-7003008f
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_0DoKZBaDcME2bmDpSJ3dZ

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-prompt-output-contract-extractor-7003008f -d '<json body>'
```

Example prompt: Analyze this request JSON and extract the output contract it defines — pull out any schema constraints, expected response formats, and output structure: {"prompt": "Summarize this article and return a JSON with fields title, summary, and sentiment", "format": "json"}

## When to prefer this

Choose this endpoint when you need to programmatically extract the implicit or explicit output contract (expected response schema, format constraints, field definitions) from a prompt or API request JSON. Best used when building agent pipelines, documentation tooling, or contract-validation layers that need to understand what structured output a given prompt demands. At $0.005 USDC per call it is cost-effective for high-volume prompt auditing workflows.

## Known failure modes

- Malformed or invalid JSON in request_json returns a parsing error
- request_json below 2 characters or above 65536 characters is rejected by schema validation
- Ambiguous or underspecified prompts may yield low-confidence extractions with warnings
- Payment failure on Base network prevents execution
- No output contract detectable in the submitted JSON returns minimal or empty analysis_json

## 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 an analysis_json field containing the extracted output contract (schema, constraints, expected format) derived from the submitted request_json, along with a warnings array noting that caller-supplied data should be verified, and an evidence_scope field indicating the data source was caller-supplied. Includes a full cryptographic receipt with payment details on 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": "prompt_output_contract_extract",
   "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": "prompt_output_contract_extract",
   "executionId": "example-execution",
   "startedAtMs": 0,
   "amountAtomic": "5000",
   "resultSha256": "7af4cc5f7368220a143b1ff501065116b4277d0af8c9535abfc00c88bf134b63",
   "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-prompt-output-contract-extractor-7003008f/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)