# SignalHarness RAG Retrieval Recall@K Evaluator

> SignalHarness RAG Retrieval Recall@K Evaluator 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).

Evaluates retrieval quality of a RAG (Retrieval-Augmented Generation) pipeline by computing Recall@K metrics from caller-supplied query and retrieved document data.

## Facts

- Endpoint: POST https://signalharness.ai/api/agent/services/rag_retrieval_recall_at_k/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-rag-retrieval-recall-k-evaluator-57d095c5
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_HtDiVJiFJqNMiC1_FQ_pa

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-rag-retrieval-recall-k-evaluator-57d095c5 -d '<json body>'
```

Example prompt: Evaluate the recall@K performance of my RAG retrieval results — here's the JSON with my queries, the ground-truth relevant documents, and the top-10 retrieved candidates per query; tell me what the recall score looks like.

## When to prefer this

Choose this endpoint when you need a fast, pay-per-call, agent-native Recall@K metric for RAG or information retrieval pipelines without standing up your own evaluation infrastructure. It is ideal for agents that need to audit retrieval quality programmatically, especially in Base USDC micropayment workflows via x402.

## Known failure modes

- Malformed or invalid `request_json` input returns a validation error
- Missing ground truth or retrieved document data leads to incomplete analysis
- Caller-supplied data quality warnings included in response when inputs cannot be fully verified
- Payment failure on the x402 protocol may prevent execution
- Empty or minimal input JSON may result in trivial or example-schema output

## 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 payload containing the computed Recall@K analysis in `analysis_json`, a service status of 'succeeded', any data quality warnings (e.g. to verify caller-supplied data), and a full receipt with payment ID, request ID, execution ID, latency, and a SHA-256 result hash for auditability.

## 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": "rag_retrieval_recall_at_k",
   "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": "rag_retrieval_recall_at_k",
   "executionId": "example-execution",
   "startedAtMs": 0,
   "amountAtomic": "10000",
   "resultSha256": "397ceca63c7c4d52dbad9b91f93f3e73659a0eb9e78aea7643719371629c1667",
   "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-rag-retrieval-recall-k-evaluator-57d095c5/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)