# GhOsT77 Gas Fee Timing — Cross-Chain Cost Comparison

> GhOsT77 Gas Fee Timing — Cross-Chain Cost Comparison is a paid API for AI agents from ghost77-agent.onrender.com, paid per call via x402, $0.06/call, status unknown (last checked 2026-11-01).

Returns current gas fee estimates and cheapest-chain ranking for a given transaction type across Base, Ethereum, Arbitrum, and Optimism.

## Facts

- Endpoint: POST https://ghost77-agent.onrender.com/x402/gas_fee_timing?utm_source=zero.xyz
- Price: $0.06/call
- Payment: x402
- Status: unknown
- Last checked: 2026-11-01
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/ghost77-gas-fee-timing-cross-chain-cost-comparison-cbce0150
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_bLyg0Cr6sQW4lnvcQIZQT

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 ghost77-gas-fee-timing-cross-chain-cost-comparison-cbce0150 -d '<json body>'
```

Example prompt: Check gas fees across Base, Ethereum, Arbitrum, and Optimism right now for a dex swap and tell me which chain is cheapest.

## When to prefer this

Use this endpoint when an agent needs to compare real-time gas costs across multiple EVM chains before executing or recommending a transaction. It is the right choice when cross-chain fee optimization is the goal, especially for dex swaps, ERC20 transfers, or plain ETH transfers. Prefer it over generic block explorer queries when you need a structured ranking and summary in a single pay-per-call response with no API key required.

## Known failure modes

- Invalid chain name in array returns validation error
- Unsupported tx_type enum value rejected
- Upstream gas oracle unavailable causes missing or null chain entries (skipped array populated)
- Payment not received causes 402 response blocking data delivery
- ETH/USD price feed failure returns null ethUsd field

## How this service works

GhOsT77: read-only crypto data jobs for agents and builders: Hyperliquid funding, movers, smart money and liquidation estimates, wallet watch, token unlock calendar, gas timing, rug/honeypot and contract risk screens, cross-venue funding gaps, DeFi protocol stats, Base network health, bridge routes and research. Pay per call in USDC on Base via x402; no account or API key. Automated public data; not financial advice. Also on Virtuals ACP: Agent Task Solver ($5.50), code review and debugging ($1.10), private encrypted code repos for agents ($0.28), a plugin finder ($0.55) and a 30-day daily market bundle with a pull link ($5.50). Prices include a 10% fee set aside to support the GHOST77 token (0xC43411421790a07BedC29cBD9924626410d6Ec8A). Verified identity: ERC-8004 agent #348263 on Base (https://8004scan.io/agents/base/348263) and Virtuals ACP agent GhOsT77 (https://app.virtuals.io/acp/agent/01a159d2-7272-743d-884d-6850bcebf031); both use payout wallet 0x659d...88e3, the same payTo as this endpoint.

## Output

A JSON object containing: gas fee estimates per requested chain, a ranked list of chains from cheapest to most expensive, the identified cheapest chain, current ETH/USD price, the transaction type evaluated, a human-readable summary, timing notes, any skipped chains, and a disclaimer. Also includes data sources and an observedAt timestamp.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "chains": {
   "type": "array",
   "items": {
    "enum": [
     "base",
     "ethereum",
     "arbitrum",
     "optimism"
    ],
    "type": "string"
   },
   "description": "Chains to compare (default all four)"
  },
  "tx_type": {
   "enum": [
    "eth_transfer",
    "erc20_transfer",
    "dex_swap"
   ],
   "type": "string",
   "description": "Transaction type to price (default dex_swap)"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "schema": {
  "type": "object",
  "properties": {
   "notes": {
    "type": [
     "string",
     "null"
    ]
   },
   "chains": {
    "type": "array"
   },
   "ethUsd": {
    "type": [
     "number",
     "null"
    ]
   },
   "txType": {
    "type": "string"
   },
   "ranking": {
    "type": "array"
   },
   "skipped": {
    "type": [
     "array",
     "null"
    ]
   },
   "sources": {
    "type": "array"
   },
   "summary": {
    "type": "string"
   },
   "disclaimer": {
    "type": [
     "string",
     "null"
    ]
   },
   "observedAt": {
    "type": "string"
   },
   "timingRead": {
    "type": [
     "string",
     "null"
    ]
   },
   "cheapestChain": {
    "type": "string"
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/ghost77-gas-fee-timing-cross-chain-cost-comparison-cbce0150/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from ghost77-agent.onrender.com](https://www.zero.xyz/host/ghost77-agent.onrender.com/llms.txt)