# SignalHarness NFT Metadata Validator

> SignalHarness NFT Metadata Validator is a paid API for AI agents from signalharness.ai, paid per call via x402, $0.005/call, status unknown (last checked 2026-09-13).

Validates NFT metadata supplied by the caller and returns structured validation results with warnings and evidence scope.

## Facts

- Endpoint: POST https://signalharness.ai/api/agent/services/nft_metadata_validate/invoke
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-13
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/signalharness-nft-metadata-validator-a574bf04
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_ljQhZijudjdwYU-yxn2SO

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-metadata-validator-a574bf04 -d '<json body>'
```

Example prompt: Can you validate this NFT metadata for me and flag any warnings or issues before I mint: '{"name":"CryptoKitty #42","description":"A rare orange tabby","image":"ipfs://Qm...","attributes":[{"trait_type":"Color","value":"Orange"}]}'?

## When to prefer this

Choose this endpoint when you need a quick, programmatic, per-call NFT metadata validation with a structured warning list and evidence scope — especially useful for pre-mint checks, marketplace submission pipelines, or automated collection auditing. At $0.005 USDC per call it is cost-effective for single-item or batch-level spot checks. Prefer this over generic JSON schema validators when you need NFT-domain-aware validation logic and a tamper-evident receipt.

## Known failure modes

- Invalid or malformed JSON string input — returns error status
- Input string too short (below minLength of 2) or too large (above maxLength of 65536)
- Payment failure or insufficient USDC balance — request blocked before execution
- Network or service unavailability — returns non-success status
- Metadata content that cannot be parsed as NFT metadata — may return empty or minimal validation result

## 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 object with a 'result' field containing: 'nft_metadata_validation' (the main validation output), 'warnings' (an array of warning strings found in the metadata), and 'evidence_scope' (indicating the data source, e.g. 'caller_supplied_data'). Also includes a 'status' field ('succeeded' on success), a signed receipt with payment and execution details, and an artifacts array.

## Request schema (JSON Schema)

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

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "replay": false,
  "result": {
   "warnings": [
    "Validation does not fetch media or authenticate the collection."
   ],
   "service_id": "nft_metadata_validate",
   "evidence_scope": "caller_supplied_data",
   "nft_metadata_validation": "{\"errors\":[],\"supplied_fields\":[\"attributes\",\"image\",\"name\"],\"valid\":true}"
  },
  "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_metadata_validate",
   "executionId": "example-execution",
   "startedAtMs": 0,
   "amountAtomic": "5000",
   "resultSha256": "529b9d3a8492c95115b1036cbe8feccc4890670969cbf582db02d8f0c2e0a01d",
   "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-metadata-validator-a574bf04/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)