# Base ERC-721 Transfer Analyze

> Base ERC-721 Transfer Analyze 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 ERC-721 NFT transfer data on Base network, parsing transfer events to identify token IDs, from/to addresses, amounts, and potential duplicate positions.

## Facts

- Endpoint: POST https://signalharness.ai/api/agent/services/base_erc721_transfer_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/base-erc-721-transfer-analyze-0491fcdd
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_63r0ahEW6KAlIT0XllQ_j

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 base-erc-721-transfer-analyze-0491fcdd -d '<json body>'
```

Example prompt: Can you analyze this ERC-721 NFT transfer data from Base — I want to know the token ID, the sender and receiver addresses, and whether there are any duplicate positions?

## When to prefer this

Use this endpoint when you need to parse and analyze ERC-721 NFT transfer events specifically on the Base (OP Stack) network. It is purpose-built for Base/Base Sepolia chain IDs and understands the OP Stack fee model and transaction types. Prefer it over generic blockchain explorers when you need structured JSON output of transfer details including duplicate position detection, and when you have raw transfer data available as JSON to submit directly.

## Known failure modes

- Invalid or malformed request_json causes parsing failure
- JSON input exceeds 65536 character limit
- Non-ERC-721 transfer data passed in produces incorrect or empty analysis
- Missing required transfer fields in input JSON lead to null values in output
- Unsupported chain ID data in input may not match accepted Base chain IDs

## 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 ERC-721 standard type, total units transferred, a list of transfer objects (each with from/to addresses, token ID, amount, operator, log index, and transaction hash), duplicate positions detected, and network context (accepted chain IDs, fee model, deposit transaction type, protocol family). Also includes evidence scope and analyzed network name, plus warnings about data limitations (e.g., does not prove current ownership).

## 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": "base_erc721_transfer_analyze",
   "analysis_json": "{\"duplicate_positions\":[],\"network_context\":{\"accepted_chain_ids\":[\"8453\",\"84532\"],\"deposit_transaction_type\":\"0x7e\",\"fee_model\":\"L2 execution plus caller-supplied L1 data/operator components\",\"protocol_family\":\"OP Stack\"},\"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": "base"
  },
  "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": "base_erc721_transfer_analyze",
   "executionId": "example-execution",
   "startedAtMs": 0,
   "amountAtomic": "10000",
   "resultSha256": "dd5de61b9ae27397b1e7bc0ba5d2c10da4dd96d57ef98014c4aad1372218ea71",
   "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/base-erc-721-transfer-analyze-0491fcdd/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)