# SignalHarness EVM Transaction Cost Comparator

> SignalHarness EVM Transaction Cost Comparator is a paid API for AI agents from signalharness.ai, paid per call via x402, $0.005/call, status unknown (last checked 2026-09-16).

Compares transaction costs across EVM networks or transaction types based on a caller-supplied description or scenario.

## Facts

- Endpoint: POST https://signalharness.ai/api/agent/services/evm_transaction_cost_compare/invoke
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-16
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/signalharness-evm-transaction-cost-comparator-3287edc1
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_zVcld8ey5zdUl3gbfneC3

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-transaction-cost-comparator-3287edc1 -d '<json body>'
```

Example prompt: Compare the transaction costs for sending 1000 USDC across Ethereum mainnet, Base, Polygon, and Arbitrum — I want to know which network is cheapest right now.

## When to prefer this

Use this endpoint when an AI agent or user needs to compare gas/transaction costs across EVM-compatible blockchains based on a described scenario, and does not have direct on-chain RPC access or a pre-built gas oracle. It is well-suited for advisory, routing, and decision-support workflows where the agent needs to recommend the cheapest chain for a specific operation type. It accepts natural language or structured descriptions, making it accessible without deep blockchain tooling knowledge.

## Known failure modes

- Malformed or empty transaction_cost_compare_request returns a validation error
- Request string exceeds 65536 character limit causing rejection
- Ambiguous or under-specified request may yield a low-confidence comparison with warnings
- Payment failure via x402 protocol results in no execution
- Network-specific data unavailable may cause partial results with warnings

## 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 JSON object containing a transaction_cost_comparison string summarizing the comparison, a list of warnings about data limitations or assumptions, the service_id confirming which service ran, and an evidence_scope field indicating the analysis was based on caller-supplied data. Also includes a full receipt with payment metadata, execution timing, and a result hash for verification.

## Request schema (JSON Schema)

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

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "replay": false,
  "result": {
   "warnings": [
    "Comparison does not forecast future gas prices."
   ],
   "service_id": "evm_transaction_cost_compare",
   "evidence_scope": "caller_supplied_data",
   "transaction_cost_comparison": "{\"cheapest\":\"a\",\"savings_vs_most_expensive_atomic\":\"420000\",\"scenarios\":[{\"cost_atomic\":\"2100000\",\"name\":\"a\"},{\"cost_atomic\":\"2520000\",\"name\":\"b\"}]}"
  },
  "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_transaction_cost_compare",
   "executionId": "example-execution",
   "startedAtMs": 0,
   "amountAtomic": "5000",
   "resultSha256": "e2d19dffc2456df880f9359378119af35d6fbb398e9f7ca639e9ebe96b6eadb0",
   "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-transaction-cost-comparator-3287edc1/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)