# SignalHarness Search Query Expander

> SignalHarness Search Query Expander 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).

Expands a set of supplied search terms into a broader, enriched set of related queries for improved search coverage

## Facts

- Endpoint: POST https://signalharness.ai/api/agent/services/search_query_expand_from_supplied_terms/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-search-query-expander-1067366e
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_OgAI_CIDi4g8EXYHvYUMu

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-search-query-expander-1067366e -d '<json body>'
```

Example prompt: Take these search terms — 'machine learning model deployment', 'MLOps', 'model serving' — and expand them into a broader set of related queries I can use to get more comprehensive search results.

## When to prefer this

Choose this endpoint when an AI agent needs to broaden its search coverage by generating related query variants from a seed set of terms, especially in agentic search loops where recall matters more than precision. It is well-suited for research, SEO, and multi-step retrieval workflows where the initial query set is narrow. At $0.01 USDC per call via x402 micropayment, it is cost-effective for repeated use in automated pipelines.

## Known failure modes

- Invalid or empty request_json causes schema validation failure
- request_json exceeds 65536 character limit returns error
- Malformed JSON string in request_json field causes parse error
- Insufficient USDC balance results in payment failure and no result
- Service returns warnings when caller-supplied data cannot be fully validated
- Network issues on Base (eip155:8453) may delay payment settlement

## 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 analysis containing expanded and related search queries derived from the supplied terms, along with a list of warnings (e.g. to verify caller-supplied data), a service_id, and a receipt confirming the successful x402 micropayment execution on Base USDC.

## 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": "search_query_expand_from_supplied_terms",
   "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": "search_query_expand_from_supplied_terms",
   "executionId": "example-execution",
   "startedAtMs": 0,
   "amountAtomic": "10000",
   "resultSha256": "eda53192d0bd5caf451b5cba46c646c305ad2e190269356948daf3d7e2380bf8",
   "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-search-query-expander-1067366e/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)