# Polygon ERC-721 Transfer Analyzer

> Polygon ERC-721 Transfer Analyzer is a paid API for AI agents from signalharness.ai, paid per call via x402, $0.01/call, status unknown (last checked 2026-09-15).

Analyzes ERC-721 NFT transfer events on the Polygon PoS network from caller-supplied evidence, extracting structured transfer details including sender, recipient, token ID, and duplicate detection.

## Facts

- Endpoint: POST https://signalharness.ai/api/agent/services/polygon_erc721_transfer_analyze/invoke
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/polygon-erc-721-transfer-analyzer-68ed65a1
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_8micyp0mVBqmt0WHrC0eg

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 polygon-erc-721-transfer-analyzer-68ed65a1 -d '<json body>'
```

Example prompt: Can you analyze this Polygon ERC-721 NFT transfer data for me and pull out the sender, receiver, and token ID — also flag any duplicate transfers if there are any?

## When to prefer this

Use this endpoint when you need to extract structured data from Polygon ERC-721 NFT transfer events from evidence you already have in hand. It is purpose-built for Polygon PoS (mainnet 137 and Amoy testnet 80002) and the ERC-721 standard specifically, with duplicate detection and network context included. Prefer this over general blockchain explorers when you need a deterministic, programmatic parse of transfer data within an agent pipeline. Not suitable for proving current ownership or querying live chain state — use a blockchain RPC for that.

## Known failure modes

- Malformed or unparseable request_json returns an error status
- Missing required transfer fields in the input may produce null values in output
- Does not prove current NFT ownership — only analyzes caller-supplied evidence
- Unsupported chain ID outside Polygon PoS (137) and Amoy testnet (80002) may produce unexpected results
- Incomplete evidence produces warnings but does not infer missing completion data

## 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 analysis JSON containing the list of ERC-721 transfers (each with from/to addresses, token ID, amount, index, operator, and transaction hash), detected duplicate positions, network context (accepted chain IDs, bridge model, completion policy, protocol family), the analyzed network name, evidence scope, any warnings (e.g. about ownership completeness), and a status field. Wrapped in a receipt with payment metadata.

## 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": [
    "Does not prove current ownership or completeness."
   ],
   "service_id": "polygon_erc721_transfer_analyze",
   "analysis_json": "{\"duplicate_positions\":[],\"network_context\":{\"accepted_chain_ids\":[\"137\",\"80002\"],\"bridge_model\":\"root-child state sync plus checkpoint evidence\",\"completion_policy\":\"never inferred without supplied evidence\",\"protocol_family\":\"Polygon PoS\"},\"standard\":\"ERC-721\",\"total_units\":\"1\",\"transfers\":[{\"amount\":\"1\",\"from\":\"0x0000000000000000000000000000000000000001\",\"index\":0,\"log_index\":null,\"operator\":null,\"to\":\"0x0000000000000000000000000000000000000002\",\"token\":null,\"token_id\":\"0\",\"transaction_hash\":null}]}",
   "evidence_scope": "caller_supplied_data",
   "analyzed_network": "polygon"
  },
  "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": "polygon_erc721_transfer_analyze",
   "executionId": "example-execution",
   "startedAtMs": 0,
   "amountAtomic": "10000",
   "resultSha256": "f121f7050176d0b19d9806b9846b9324f287567a3095500aba08880f97265918",
   "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/polygon-erc-721-transfer-analyzer-68ed65a1/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)