# true402 Base Chain Transaction Preflight

> true402 Base Chain Transaction Preflight is a paid API for AI agents from true402.dev, paid per call via x402, $0.008/call, status unknown (last checked 2026-09-14).

Simulates a Base blockchain transaction to predict gas costs, revert reasons, and execution outcomes before submission.

## Facts

- Endpoint: POST https://true402.dev/api/v1/base/tx-preflight
- Price: $0.008/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/true402-base-chain-transaction-preflight-ee8c5df5
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_bs0Cply__D6Hz2yJxFufh

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 true402-base-chain-transaction-preflight-ee8c5df5 -d '<json body>'
```

Example prompt: Before I send this contract call, simulate it on Base: from address 0xAbC123... to contract 0xDeF456..., with calldata 0xa9059cbb000000... and 0 wei value — will it succeed or revert?

## When to prefer this

Use this endpoint when you need to validate a Base blockchain transaction before broadcasting — especially for smart contract interactions where revert risk is high, or when estimating gas costs without spending funds. Prefer this over generic Ethereum mainnet simulators when targeting Base (Coinbase L2). Ideal for AI agents managing wallets that need confidence in transaction safety before committing.

## Known failure modes

- Invalid or malformed Ethereum address in 'to' or 'from' fields — returns validation error
- Malformed calldata hex string — returns parse error
- Simulation reverts due to insufficient balance, bad calldata, or contract logic — revert reason returned in response
- Node or RPC unavailability causing simulation timeout
- 'from' address has no on-chain state, affecting simulation accuracy

## How this service works

The machine-native marketplace. Wallet = identity. Pay per call with HTTP 402.

## Output

Returns a simulation result object indicating whether the transaction would succeed or revert, predicted gas usage, any revert reason or error message, and execution trace details for the given Base chain transaction parameters.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "required": [
  "to",
  "from"
 ],
 "properties": {
  "to": {
   "type": "string",
   "description": "Destination contract or address"
  },
  "data": {
   "type": "string",
   "description": "Calldata hex (0x…); omit for a plain native transfer"
  },
  "from": {
   "type": "string",
   "description": "Sender address. Asserted, never proven — no signature is taken."
  },
  "value": {
   "type": "string",
   "description": "Native value in wei as a decimal string; default 0"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "object"
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/true402-base-chain-transaction-preflight-ee8c5df5/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from true402.dev](https://www.zero.xyz/host/true402.dev/llms.txt)