# SignalHarness EVM Block Continuity

> SignalHarness EVM Block Continuity 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).

Analyzes EVM blockchain data to assess block continuity, detecting gaps or anomalies in block sequences from caller-supplied data.

## Facts

- Endpoint: POST https://signalharness.ai/api/agent/services/evm_block_continuity/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-evm-block-continuity-4e4d8fe9
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap__GaVYMpP_k8iQWa_koxUw

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-evm-block-continuity-4e4d8fe9 -d '<json body>'
```

Example prompt: Can you check whether the EVM block data I've collected has any continuity gaps or anomalies? Here's the block sequence payload: [block_continuity_request data].

## When to prefer this

Choose this endpoint when you need a dedicated, agent-native service to programmatically verify EVM block sequence continuity from caller-supplied data, especially in automated pipelines where auditability (receipt, result hash, settlement reference) matters. Prefer this over general-purpose blockchain explorers when you need a structured JSON response with explicit continuity verdict, warnings, and cryptographic receipt — particularly useful in smart contract audit workflows, indexer validation, and on-chain event replay verification.

## Known failure modes

- Malformed or empty block_continuity_request string returns a validation error
- Block data outside supported EVM format may yield inconclusive or warning-heavy results
- Payment failure via x402 protocol results in 402 response before execution
- Request exceeding 65536 character limit is rejected
- Ambiguous or incomplete block data may return warnings without a definitive continuity verdict

## 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 containing a block_continuity field with the continuity assessment result, a list of warnings if anomalies are found, the evidence_scope indicating the data source analyzed, a replay flag, and a full receipt with payment ID, execution ID, latency metrics, result hash, and settlement reference for auditability.

## Request schema (JSON Schema)

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

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "replay": false,
  "result": {
   "warnings": [
    "Continuity does not establish canonical-chain membership."
   ],
   "service_id": "evm_block_continuity",
   "evidence_scope": "caller_supplied_data",
   "block_continuity": "{\"breaks\":[],\"checked_links\":1,\"continuous\":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": "evm_block_continuity",
   "executionId": "example-execution",
   "startedAtMs": 0,
   "amountAtomic": "5000",
   "resultSha256": "885982eac563ff6f6ff9af731f62d2f7dd18d68cb4af6dfe40b6c58f696911c3",
   "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-evm-block-continuity-4e4d8fe9/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)