# Gas Oracle — Multi-Chain Fee Estimator

> Gas Oracle — Multi-Chain Fee Estimator is a paid API for AI agents from 4yearcycle.com, paid per call via x402, $0.005/call, status unknown (last checked 2026-09-13).

Returns current gas fee estimates for Base, Ethereum, and/or Bitcoin networks in a single call.

## Facts

- Endpoint: GET https://4yearcycle.com/x402/gas-oracle
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-13
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/gas-oracle-multi-chain-fee-estimator-e281421f
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap__2_oKe5HK6yY-lg8MniSg

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 gas-oracle-multi-chain-fee-estimator-e281421f
```

Example prompt: What are the current gas fees on Ethereum and Base, and what's the fast sat/vB rate for Bitcoin right now?

## When to prefer this

Choose this endpoint when you need real-time gas fee data across Base, Ethereum, and/or Bitcoin in a single lightweight call. It is ideal for wallets, trading bots, or automation agents that need to select an appropriate fee tier before broadcasting a transaction. Prefer it over chain-specific RPC calls when you need multi-chain coverage simultaneously, or when you need Bitcoin sat/vB estimates alongside EVM gwei data in one response.

## Known failure modes

- Invalid chain name in query param returns an error or empty results
- Upstream RPC or mempool.space outage may cause stale or missing chain data
- Malformed chains query param (wrong delimiter or unsupported alias) may be rejected
- Payment of 0.005 USDC not provided or x402 handshake fails — returns 402 Payment Required
- Network timeout from upstream RPC results in missing chain entry

## How this service works

Interactive Bitcoin 4-year halving cycle chart on a polar disc. Live price, 200W MA, Mayer Multiple, RSI, MACD, Pi Cycle and optional paid cycle projections.

## Output

A JSON object containing a count of chains queried and an array of per-chain fee objects. EVM chains (Base, Ethereum) include baseFeeGwei, gasPriceGwei, priorityGwei tiers (fast/normal/slow), and the RPC endpoint used. Bitcoin includes satPerVb tiers (fast/normal/slow/minimum). All entries include the chain name, kind (evm or btc), and fetchedAt epoch timestamp. Data is cached server-side for 60 seconds.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [],
     "properties": {
      "chains": {
       "type": "string",
       "default": "base,ethereum,bitcoin",
       "pattern": "^[a-z]+(,[a-z]+)*$",
       "examples": [
        "base,ethereum,bitcoin",
        "base",
        "eth,btc"
       ],
       "description": "Comma-separated chains to quote: base, ethereum (alias eth), bitcoin (alias btc). Default: base,ethereum,bitcoin."
      }
     },
     "additionalProperties": false
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "required": [
      "count",
      "chains"
     ],
     "properties": {
      "count": {
       "type": "integer",
       "description": "Number of chain quotes returned"
      },
      "chains": {
       "type": "array",
       "items": {
        "type": "object",
        "required": [
         "chain",
         "kind",
         "fetchedAt"
        ],
        "properties": {
         "rpc": {
          "type": "string",
          "description": "EVM only: which public RPC answered"
         },
         "kind": {
          "enum": [
           "evm",
           "btc"
          ],
          "type": "string",
          "description": "Fee model: evm = gwei fields, btc = satPerVb field"
         },
         "chain": {
          "type": "string",
          "description": "Canonical chain name: base, ethereum or bitcoin"
         },
         "satPerVb": {
          "type": "object",
          "properties": {
           "fast": {
            "type": "number"
           },
           "slow": {
            "type": "number"
           },
           "normal": {
            "type": "number"
           },
           "minimum": {
            "type": "number"
           }
          },
          "description": "Bitcoin only: fee-rate tiers in sat/vB from mempool.space (slow ≈ 1h, normal ≈ 30min, fast = next block)"
         },
         "fetchedAt": {
          "type": "integer",
          "des
… (truncated)
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "count": 3,
  "chains": [
   {
    "rpc": "https://mainnet.base.org",
    "kind": "evm",
    "chain": "base",
    "fetchedAt": 1787054938980,
    "baseFeeGwei": 0.005,
    "gasPriceGwei": 0.006,
    "priorityGwei": {
     "fast": 0.0085,
     "slow": 0,
     "normal": 0.001
    }
   },
   {
    "rpc": "https://ethereum-rpc.publicnode.com",
    "kind": "evm",
    "chain": "ethereum",
    "fetchedAt": 1787054938937,
    "baseFeeGwei": 0.06,
    "gasPriceGwei": 0.0572,
    "priorityGwei": {
     "fast": 1,
     "slow": 0.0001,
     "normal": 0.0054
    }
   },
   {
    "kind": "btc",
    "chain": "bitcoin",
    "satPerVb": {
     "fast": 2,
     "slow": 1,
     "normal": 1,
     "minimum": 1
    },
    "fetchedAt": 1787054938881
   }
  ]
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/gas-oracle-multi-chain-fee-estimator-e281421f/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from 4yearcycle.com](https://www.zero.xyz/host/4yearcycle.com/llms.txt)