# x402node Transaction Gas Cost Estimator

> x402node Transaction Gas Cost Estimator is a paid API for AI agents from api.x402node.dev, paid per call via x402, $0.005/call, status unknown (last checked 2026-09-15).

Estimates the USD cost of a blockchain transaction (transfer, ERC20 transfer, approve, swap, NFT mint) on Base, Ethereum, Arbitrum, Optimism, or Polygon using live gas prices and native token prices.

## Facts

- Endpoint: GET https://api.x402node.dev/chain/tx-cost
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/x402node-transaction-gas-cost-estimator-93e542c8
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_VBnHVrvgcKHhIFJUMbrAe

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 x402node-transaction-gas-cost-estimator-93e542c8
```

Example prompt: Before I do this token swap on Base, can you estimate how much the transaction will cost in USD right now using live gas prices?

## When to prefer this

Use this endpoint when an AI agent needs to evaluate the economic viability of a blockchain transaction before committing to it — especially for DeFi workflows where gas costs can make small trades unprofitable. Ideal for pre-flight checks on Base, Ethereum, Arbitrum, Optimism, or Polygon. Prefer this over generic gas trackers because it returns a direct USD estimate for specific operation types.

## Known failure modes

- Unsupported chain name returns 400 or error
- Unsupported transaction type returns 400
- RPC or gas oracle unavailable causes 503 or timeout
- Native token price feed unavailable causes stale or failed estimate
- Invalid parameters return 422 validation error

## How this service works

Estimate the USD cost of a transaction (transfer, ERC20 transfer, approve, swap, NFT mint) on Base/Ethereum/Arbitrum/Optimism/Polygon from live gas price and native token price - lets agents decide whether an action is worth the fee before sending. gas cost, transaction cost, tx fee usd, how much gas, operation cost, fee estimate

## Output

Returns an estimated USD cost for the specified transaction type on the chosen EVM chain, derived from live gas prices and the current native token (ETH/MATIC) price. Includes breakdown of gas units, gas price in gwei, native token price, and final USD cost so the agent can decide whether proceeding is economically justified.

## Example request

```json
{
 "chain": "base",
 "txType": "transfer",
 "gasLimit": 21000
}
```

## 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": {
      "chain": {
       "type": "string",
       "description": "base (default), ethereum, arbitrum, optimism, polygon"
      },
      "gasLimit": {
       "type": "string",
       "description": "Optional custom gas limit"
      },
      "operation": {
       "type": "string",
       "description": "transfer, erc20transfer, approve, swap (default), nftmint, nfttransfer"
      }
     }
    }
   },
   "additionalProperties": false
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/x402node-transaction-gas-cost-estimator-93e542c8/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.x402node.dev](https://www.zero.xyz/host/api.x402node.dev/llms.txt)