# Base Nonce Replacement Analyzer

> Base Nonce Replacement Analyzer is a paid API for AI agents from signalharness.ai, paid per call via x402, $0.015/call, status unknown (last checked 2026-09-15).

Analyzes a set of Base (OP Stack) transactions to detect nonce gaps, replacement groups, and sequencing anomalies from caller-supplied transaction data.

## Facts

- Endpoint: POST https://signalharness.ai/api/agent/services/base_nonce_replacement_analyze/invoke
- Price: $0.015/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/base-nonce-replacement-analyzer-4aeed8bb
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_kSS6Ykr8XRQoWcGpziWFg

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-nonce-replacement-analyzer-4aeed8bb -d '<json body>'
```

Example prompt: Can you analyze these Base mainnet transactions for nonce gaps and replacement groups? Here's the JSON: [{"from":"0xAbC...","hash":"0x111...","index":0,"nonce":"5","max_fee_per_gas":"120"}]

## When to prefer this

Choose this endpoint when you need to programmatically analyze a set of Base L2 (OP Stack) transactions for nonce sequencing issues, replacement patterns, or gaps — especially when debugging stuck or dropped transactions from wallets or bots. It is well-suited for agent workflows that already have raw transaction metadata and need structured classification without making direct RPC calls. Prefer alternatives that query live chain state if canonical confirmation of replacement is required.

## Known failure modes

- Malformed or non-JSON request_json causes validation failure
- Missing required transaction fields (hash, nonce, from) results in incomplete analysis
- Canonical replacement status cannot be confirmed without on-chain evidence — analysis is limited to caller-supplied data
- Very large transaction sets may hit the 65536-character input limit
- Chain IDs outside Base (8453) or Base Sepolia (84532) may produce unexpected results

## 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 detected nonce gaps, replacement transaction groups, per-transaction metadata (hash, nonce, from address, gas params), the inferred network context (chain IDs, fee model, protocol family), an evidence scope label, any warnings about limitations, and a service receipt with payment confirmation details.

## 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": [
    "Canonical replacement status requires chain evidence not inferred here."
   ],
   "service_id": "base_nonce_replacement_analyze",
   "analysis_json": "{\"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\"},\"nonce_gaps\":[],\"replacement_groups\":[],\"transactions\":[{\"from\":\"0x0000000000000000000000000000000000000001\",\"hash\":\"0x1111111111111111111111111111111111111111111111111111111111111111\",\"index\":0,\"max_fee_per_gas\":\"120\",\"nonce\":\"1\"}]}",
   "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_nonce_replacement_analyze",
   "executionId": "example-execution",
   "startedAtMs": 0,
   "amountAtomic": "15000",
   "resultSha256": "8c7f4d7e9f511cec78ba553c86dbbbdb04e2f6e9886e7054271c663940a52c1f",
   "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-nonce-replacement-analyzer-4aeed8bb/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)