# x402 Gas Fee Oracle

> x402 Gas Fee Oracle is a paid API for AI agents from x402-tools-production-2755.up.railway.app, paid per call via x402, $0.002/call, status unknown (last checked 2026-10-02).

Returns live EIP-1559 gas fee tiers (slow/standard/fast) with USD cost estimates for common transaction types across up to 6 EVM chains, sorted cheapest first

## Facts

- Endpoint: GET https://x402-tools-production-2755.up.railway.app/tools/gas?utm_source=zero.xyz
- Price: $0.002/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-02
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/x402-gas-fee-oracle-a09003bf
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_iZxIfYw3fCfBfj0kropj6

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 x402-gas-fee-oracle-a09003bf
```

Example prompt: Before I send this swap, check current gas fees across Ethereum, Base, Arbitrum, Optimism, Polygon, and BSC — give me the slow/standard/fast EIP-1559 tiers with USD costs for a swap on each chain, sorted by cheapest first.

## When to prefer this

Use this endpoint when an agent needs to programmatically choose the most cost-efficient EVM chain or fee tier before submitting a transaction. It is preferred over manual RPC calls because it aggregates live data from 6 chains in one request, converts fees to USD, and ranks chains by cost — eliminating the need to query each chain separately and compute USD conversions.

## Known failure modes

- Upstream RPC node unavailable for a specific chain — that chain may be omitted from results
- Stale data if block production is slow on a chain
- Invalid chain name in query param returns error or is silently ignored
- Network timeout if multiple chains are queried simultaneously under load

## How this service works

Use before sending an EVM transaction to pick the cheapest chain and set its fees. Live gas on Ethereum, Base, Arbitrum, Optimism, Polygon and BSC: slow/standard/fast EIP-1559 fee tiers (priority fee, maxFee) from recent blocks, plus the USD cost of a transfer, ERC-20 transfer and swap per tier, cheapest chain first.

## Output

A list of EVM chains sorted cheapest-first, each with slow/standard/fast EIP-1559 fee tiers (priority fee and maxFee in gwei), plus estimated USD costs for a native transfer, ERC-20 transfer, and swap at each speed tier, derived from recent block data.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "properties": {
      "chains": {
       "type": "string",
       "description": "Comma-separated subset of: ethereum, base, arbitrum, optimism, polygon, bsc. Default: all"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/x402-gas-fee-oracle-a09003bf/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from x402-tools-production-2755.up.railway.app](https://www.zero.xyz/host/x402-tools-production-2755.up.railway.app/llms.txt)