# SignalHarness Prompt Diff Analyzer

> SignalHarness Prompt Diff Analyzer is a paid API for AI agents from signalharness.ai, paid per call via x402, $0.01/call, status unknown (last checked 2026-09-13).

Analyzes differences and changes between two prompt versions or prompt-related JSON structures, returning structured analysis results.

## Facts

- Endpoint: POST https://signalharness.ai/api/agent/services/prompt_diff_analyze/invoke
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-13
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/signalharness-prompt-diff-analyzer-7cfd833b
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_6ChHqSBxVz3NGOFo7bz1N

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-diff-analyzer-7cfd833b -d '<json body>'
```

Example prompt: Can you diff these two versions of my system prompt and tell me what changed? Here's the JSON: {"before": "You are a helpful assistant.", "after": "You are a helpful, concise assistant. Do not use bullet points."}

## When to prefer this

Choose this endpoint when you need a quick, pay-per-call ($0.01 USDC) analysis of prompt differences without standing up your own diff infrastructure. Ideal for AI agent workflows that need to programmatically audit, compare, or validate prompt changes in a structured JSON format. Prefer this over manual diffing when the output needs to be machine-readable and traceable via receipt.

## Known failure modes

- Malformed or invalid JSON in request_json field returns an error
- Input string shorter than 2 characters or longer than 65536 characters is rejected
- Missing required request_json property causes validation failure
- Payment failure on x402 network prevents execution
- Caller-supplied data that cannot be parsed as valid prompt diff structure may yield unreliable analysis with warnings

## 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 an analysis_json field with the structured diff or analysis results, a warnings array (e.g. reminders to verify caller-supplied data), the service_id, and an evidence_scope indicator. Also includes a full receipt with payment metadata (paymentId, receiptId, network, amountAtomic, resultSha256) and execution timing details.

## 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_diff_analyze",
   "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_diff_analyze",
   "executionId": "example-execution",
   "startedAtMs": 0,
   "amountAtomic": "10000",
   "resultSha256": "df7ddac984cce5812235b704d5530b3240c3d3cd6382bac0fc3a807551965456",
   "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-diff-analyzer-7cfd833b/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)