# Polygon Checkpoint Data Inspector

> Polygon Checkpoint Data Inspector is a paid API for AI agents from signalharness.ai, paid per call via x402, $0.015/call, status unknown (last checked 2026-09-13).

Analyzes and extracts structured metadata from Polygon PoS checkpoint data supplied by the caller, including block range, Merkle root presence, and monotonicity checks.

## Facts

- Endpoint: POST https://signalharness.ai/api/agent/services/polygon_checkpoint_data_inspect/invoke
- Price: $0.015/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-13
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/polygon-checkpoint-data-inspector-304905ce
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_PMdjpl9HPUaTMKgkyd8Hx

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-checkpoint-data-inspector-304905ce -d '<json body>'
```

Example prompt: I have this Polygon PoS checkpoint JSON payload — can you inspect it and tell me the block range, whether the Merkle root is present, and if the block sequence is monotonic?

## When to prefer this

Choose this endpoint when you need to programmatically parse and extract structured metadata from a Polygon PoS checkpoint payload you already have in hand — especially block range, root presence, and network context — without needing on-chain signature verification or finality confirmation. It is ideal for offline analysis, bridge auditing, or debugging checkpoint data at $0.015 per call.

## Known failure modes

- Malformed or non-JSON input in request_json returns an error or unexpected analysis
- Checkpoint data missing required fields may produce warnings rather than a hard error
- No signature verification is performed — the service explicitly warns it does not verify Ethereum inclusion or finalized checkpoint status
- Unsupported chain IDs outside 137/80002 may yield incomplete network context
- Oversized payloads exceeding 65536 characters will be rejected by schema validation

## 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 JSON analysis of the supplied Polygon checkpoint data, including block count, start and end block numbers, monotonicity flag, Merkle root value and presence flag, accepted chain IDs (137 for mainnet, 80002 for Amoy testnet), bridge model description, signature verification status (always false — no on-chain verification performed), and any warnings. Also includes a receipt with payment ID, execution timing, and a SHA-256 hash of the result.

## 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 verify signatures, Ethereum inclusion, or finalized checkpoint status."
   ],
   "service_id": "polygon_checkpoint_data_inspect",
   "analysis_json": "{\"block_count\":\"10\",\"end_block\":\"10\",\"monotonic\":true,\"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\"},\"root\":\"0x1111111111111111111111111111111111111111111111111111111111111111\",\"root_present\":true,\"signature_verification_performed\":false,\"start_block\":\"1\"}",
   "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_checkpoint_data_inspect",
   "executionId": "example-execution",
   "startedAtMs": 0,
   "amountAtomic": "15000",
   "resultSha256": "9f8e0105cbda7f86c3461e9c46a9d62f6b72478c1ed3e514b996a9ff1df08cb4",
   "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-checkpoint-data-inspector-304905ce/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)