# SignalHarness Crosschain Event Timeline

> SignalHarness Crosschain Event Timeline is a paid API for AI agents from signalharness.ai, paid per call via x402, $0.025/call, status unknown (last checked 2026-09-15).

Sorts and analyzes a caller-supplied list of blockchain events across multiple chains (Solana, Base, Polygon) into a unified, ordered timeline, detecting ordering ambiguities.

## Facts

- Endpoint: POST https://signalharness.ai/api/agent/services/crosschain_event_timeline/invoke
- Price: $0.025/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/signalharness-crosschain-event-timeline-b2da634e
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_mjEotGRSAyW4k9T1bXsXn

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-crosschain-event-timeline-b2da634e -d '<json body>'
```

Example prompt: I have a list of blockchain events across Solana, Base, and Polygon — can you sort them into a single unified timeline and flag any ordering ambiguities? Here are the events as JSON: [{"chain":"solana","block_number":1,"transaction_index":0,"log_index":0,"address":"0x000...001"},{"chain":"base","block_number":5000,"transaction_index":1,"log_index":0,"address":"0x000...002"}]

## When to prefer this

Use this endpoint when you have a caller-supplied set of raw blockchain events spanning multiple chains (Solana, Base, Polygon) and need them sorted, deduplicated, and analyzed for ordering ambiguity in a single API call. It is particularly useful for DeFi audits, bridge transaction verification, and multichain wallet reconstruction where you already hold the raw event data and need structured ordering analysis without querying a node directly.

## Known failure modes

- Malformed or non-JSON input in request_json returns a parse error
- Events with missing required fields (chain, block_number) may cause incomplete analysis
- Caller-supplied timestamps are not independently verified — ordering may be incorrect if input data is wrong
- Unsupported chain identifiers may be ignored or cause warnings
- Exceeding the 65536-character input limit results in rejection

## 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 a sorted array of events tagged by chain, block number, transaction index, and log index; an ambiguous_order boolean flag; the total event count; the set of analyzed networks; and any warnings (e.g. that clock and ordering evidence are caller-supplied). The result is wrapped in a standard SignalHarness receipt with payment and execution metadata.

## 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": [
    "Clock and ordering evidence are caller supplied."
   ],
   "service_id": "crosschain_event_timeline",
   "analysis_json": "{\"ambiguous_order\":false,\"count\":1,\"events\":[{\"_source_index\":0,\"address\":\"0x0000000000000000000000000000000000000001\",\"block_number\":1,\"chain\":\"solana\",\"log_index\":0,\"transaction_index\":0}]}",
   "evidence_scope": "caller_supplied_data",
   "analyzed_network": "solana_base_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": "crosschain_event_timeline",
   "executionId": "example-execution",
   "startedAtMs": 0,
   "amountAtomic": "25000",
   "resultSha256": "ecd612d299676c91bf94d60fbc1299d5ff24af4493da4d6cbaf86cfbeb0f9ca5",
   "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-crosschain-event-timeline-b2da634e/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)