# SignalHarness Base Event Sequence Analyzer

> SignalHarness Base Event Sequence Analyzer is a paid API for AI agents from signalharness.ai, paid per call via x402, $0.015/call, status unknown (last checked 2026-09-14).

Analyzes and orders a sequence of Base blockchain events, resolving ambiguities in event ordering and returning structured analysis with chain context.

## Facts

- Endpoint: POST https://signalharness.ai/api/agent/services/base_event_sequence_analyze/invoke
- Price: $0.015/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/signalharness-base-event-sequence-analyzer-4d131244
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_4c09l40wUkXBFAISaML4T

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-base-event-sequence-analyzer-4d131244 -d '<json body>'
```

Example prompt: Analyze the ordering of these Base blockchain events for me — I have a set of logs with block numbers, transaction indexes, and log indexes, and I need to know if their sequence is unambiguous and what the correct order is.

## When to prefer this

Use this endpoint when you have a set of raw Base blockchain event logs and need to determine their canonical ordering or detect ordering ambiguity. It is purpose-built for Base (chain ID 8453) and Base Sepolia (84532) with OP Stack-aware context, making it more appropriate than generic EVM log parsers when working specifically on Base. Ideal for agents auditing DeFi transactions, debugging smart contract interactions, or building reliable event-driven pipelines on Base.

## Known failure modes

- Missing or malformed request_json causes validation error
- Events without required block/transaction/log indexes may produce unreliable ordering
- Supplying events from unsupported chain IDs (not 8453 or 84532) may return an error or unrecognized network
- Empty event list may return empty analysis
- Extremely large event arrays may exceed maxLength constraint on request_json

## 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 analysis including whether event ordering is ambiguous, the count of events, an ordered list of events with their source index, address, block number, chain ID, log index, and transaction index, plus network context for Base (accepted chain IDs, deposit transaction type, fee model, and OP Stack protocol family). Also returns evidence scope and analyzed network identifier.

## 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": [
    "Ordering relies on supplied block/transaction/log indexes."
   ],
   "service_id": "base_event_sequence_analyze",
   "analysis_json": "{\"ambiguous_order\":false,\"count\":1,\"events\":[{\"_source_index\":0,\"address\":\"0x0000000000000000000000000000000000000001\",\"block_number\":1,\"chain\":\"8453\",\"log_index\":0,\"transaction_index\":0}],\"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\"}}",
   "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_event_sequence_analyze",
   "executionId": "example-execution",
   "startedAtMs": 0,
   "amountAtomic": "15000",
   "resultSha256": "63250bafa752cc7ac2e6c3887baf92a5b318588976e94347d0fc1baba966c87f",
   "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-base-event-sequence-analyzer-4d131244/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)