# Base Mainnet Transaction Gas Preflight Simulator

> Base Mainnet Transaction Gas Preflight Simulator is a paid API for AI agents from api.nexismvp.com, paid per call via x402, $0.001/call, status unknown (last checked 2026-09-14).

Simulates a Base mainnet transaction before submission using eth_estimateGas and eth_call, returning success/failure prediction, estimated gas units, and estimated cost.

## Facts

- Endpoint: POST https://api.nexismvp.com/market/gas-preflight
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/base-mainnet-transaction-gas-preflight-simulator-4bfd4a01
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_A3pZ6Ond0iPsEToyxG-Rk

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 base-mainnet-transaction-gas-preflight-simulator-4bfd4a01 -d '<json body>'
```

Example prompt: Before I submit this transaction, can you run a preflight simulation on Base mainnet to check if it'll succeed and tell me the estimated gas cost? The to address is 0xAbC123..., the calldata is 0xa9059cbb000..., and I'm sending 0 ETH value.

## When to prefer this

Choose this endpoint when you need to verify a Base mainnet transaction will succeed and estimate its gas cost before committing to an on-chain submission. Ideal for agents managing smart contract interactions, DeFi operations, or any workflow where a failed transaction would waste gas fees. Prefer this over generic Ethereum gas estimators when working specifically on Base L2.

## Known failure modes

- Invalid or malformed 'to' address returns validation error
- Malformed calldata causes eth_call revert with revert reason if available
- Missing POST body fields results in 400 error
- Base mainnet RPC unavailability causes timeout or 503
- Transactions that would revert return success: false with revert reason
- Value exceeds simulated sender balance may cause revert in simulation

## How this service works

Simulate a Base mainnet transaction before submitting it — real eth_estimateGas + eth_call against the given {to, data, value}, returns whether it would succeed, estimated gas, and estimated cost. POST body required. Experimental/informational only — not financial advice.

## Output

Returns whether the simulated transaction would succeed or revert on Base mainnet, the estimated gas units required, and the estimated cost in ETH/USD — all derived from a real eth_estimateGas and eth_call against Base mainnet state, without actually broadcasting the transaction.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "to": {
   "type": "string",
   "description": "Target address"
  },
  "data": {
   "type": "string",
   "description": "Call data, 0x-prefixed hex (default 0x)"
  },
  "chain": {
   "enum": [
    "base"
   ],
   "type": "string",
   "description": "Only 'base' supported currently"
  },
  "value": {
   "type": "string",
   "description": "Value in wei, 0x-prefixed hex (default 0x0)"
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/base-mainnet-transaction-gas-preflight-simulator-4bfd4a01/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.nexismvp.com](https://www.zero.xyz/host/api.nexismvp.com/llms.txt)