# SignalHarness NFT Collection Change Detector

> SignalHarness NFT Collection Change Detector is a paid API for AI agents from signalharness.ai, paid per call via x402, $0.01/call, status unknown (last checked 2026-09-16).

Analyzes a described NFT collection and identifies or reports changes, events, or shifts in that collection based on caller-supplied data.

## Facts

- Endpoint: POST https://signalharness.ai/api/agent/services/nft_collection_change/invoke
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-16
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/signalharness-nft-collection-change-detector-5044bc8e
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_Ql6arz5KEd12EajXcNRt_

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-nft-collection-change-detector-5044bc8e -d '<json body>'
```

Example prompt: Can you check what's changed recently in the Bored Ape Yacht Club NFT collection — things like new listings, sales, or ownership shifts?

## When to prefer this

Choose this endpoint when you need to extract or summarize changes in an NFT collection based on a textual or structured description of the collection and its recent events, especially in an agent-native workflow where micropayment-per-call (x402) is acceptable. It is well-suited for on-demand, single-call NFT change analysis rather than continuous streaming monitoring.

## Known failure modes

- Empty or too-short request string (minLength:2 not met) returns validation error
- Ambiguous or insufficient collection description may produce empty or low-confidence change results
- Network or payment settlement failure returns non-succeeded status in receipt
- Service unavailability returns error status with no result body

## 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 structured result containing identified NFT collection changes derived from the caller-supplied request description, along with any warnings about data limitations, an evidence scope indicator ('caller_supplied_data'), and a signed receipt with payment and execution metadata confirming the call was processed.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "nft_collection_change_request": {
   "type": "string",
   "maxLength": 65536,
   "minLength": 2
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "replay": false,
  "result": {
   "warnings": [
    "Snapshots are caller supplied and not chain verified."
   ],
   "service_id": "nft_collection_change",
   "evidence_scope": "caller_supplied_data",
   "nft_collection_changes": "{\"added\":[\"2\"],\"changed\":[\"1\"],\"removed\":[],\"unchanged_count\":0}"
  },
  "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": "nft_collection_change",
   "executionId": "example-execution",
   "startedAtMs": 0,
   "amountAtomic": "10000",
   "resultSha256": "48b6b88108aadad1e8bcafcd1752aa94bc9f3254c1bf88ecaedb6b2cfa837c1e",
   "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-nft-collection-change-detector-5044bc8e/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)