# SignalHarness CrossChain Fee Comparator

> SignalHarness CrossChain Fee Comparator 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).

Compares transaction fees across multiple blockchain networks (Base, Solana, Polygon) for a given set of on-chain operations using caller-supplied data.

## Facts

- Endpoint: POST https://signalharness.ai/api/agent/services/crosschain_fee_compare/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/signalharness-crosschain-fee-comparator-099dea13
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_CxvDOVZ_JLCj847slfZLY

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-fee-comparator-099dea13 -d '<json body>'
```

Example prompt: Compare the transaction fees for my transfer across Base, Solana, and Polygon — I have fee amounts in wei for Base (2205000) and SOL lamports for Solana, and I need to know which chain is cheapest.

## When to prefer this

Use this endpoint when you have fee data from multiple blockchains (especially Base, Solana, and Polygon) and need a structured, policy-driven comparison to determine the lowest-cost chain for a transaction. Prefer it over manual comparisons or single-chain fee estimators when operating cross-chain and needing an auditable, machine-readable ranking with an evidence scope. Ideal for AI agents making autonomous routing decisions about which chain to settle on.

## Known failure modes

- Missing or malformed request_json causes immediate validation failure
- Cross-asset fee ranking without supplied conversion values triggers a warning and may produce incomplete results
- Unsupported or unrecognized chain identifiers may be silently excluded from analysis
- Stale or missing timestamps on fee data produce unreliable comparisons
- Payment failure (insufficient USDC balance) results in 402 response and no analysis

## 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 object containing a comparison policy, a list of fees per chain with amounts and units, the set of analyzed networks (e.g. solana_base_polygon), an evidence scope label (caller_supplied_data), and any warnings about cross-asset ranking or missing conversion values. Also includes a 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": [
    "Cross-asset ranking requires supplied conversion values and timestamps."
   ],
   "service_id": "crosschain_fee_compare",
   "analysis_json": "{\"comparison_policy\":\"compare_only_identical_units_or_caller_supplied_conversions\",\"fees\":[{\"amount\":\"2205000\",\"chain\":\"base\",\"unit\":\"wei\"}]}",
   "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_fee_compare",
   "executionId": "example-execution",
   "startedAtMs": 0,
   "amountAtomic": "15000",
   "resultSha256": "77b4bdd5eace6f77d9b15b745949c3cfca46fe6a2637f50590d2abd6774e231d",
   "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-fee-comparator-099dea13/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)