# Vextorium Build EVM Transaction

> Vextorium Build EVM Transaction is a paid API for AI agents from api.vextorium.com, paid per call via x402, $0.004/call, status unknown (last checked 2026-10-19).

Builds an unsigned EVM transaction (native transfer, ERC-20 transfer, or ERC-20 approve) with full fields, gas estimate, EIP-1559 fees, and revert simulation — ready to sign but never submitted.

## Facts

- Endpoint: POST https://api.vextorium.com/v1/build-transaction?utm_source=zero.xyz
- Price: $0.004/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-19
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/vextorium-build-evm-transaction-01f9b82f
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_licr9y7azO4prR-1H-DVp

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 vextorium-build-evm-transaction-01f9b82f -d '<json body>'
```

Example prompt: Build me an unsigned ERC-20 transfer transaction to send 100 USDC from 0xd8dA6BF26964aF9D7eed9e03E53415D37aA96045 to 0x9b9b3f22bebd1e3e528c2759a2ca34cd2e0184a1 on the Base network — I want to see the gas estimate, EIP-1559 fees, and whether it would revert before I sign it.

## When to prefer this

Choose this endpoint when an agent needs to construct and inspect a transaction before signing — especially when you want gas estimates, EIP-1559 fee data, and a revert simulation all in one call without any risk of broadcasting. Prefer this over on-chain submission endpoints when the user's wallet signs independently, or when you need to present a cost preview before committing. It supports native transfers, ERC-20 transfers, and ERC-20 approvals across EVM-compatible chains.

## Known failure modes

- Invalid or unsupported network name returns an error
- Unrecognized token address or symbol fails lookup
- Malformed sender/recipient address causes validation error
- Action type not matching token context (e.g. native_transfer with a token address) may error
- Simulation result indicates revert — transaction would fail on-chain
- Missing required fields (since, action, for, amount) returns schema validation error
- Network RPC unavailability causes timeout or error response

## How this service works

558 pay-per-call data APIs for AI agents: Solana and EVM on-chain data, tokenized stocks, DeFi, Hyperliquid, economy and official statistics, FX, validation, web and developer tools. Pay in USDC via x402.

## Output

Returns a complete unsigned transaction object (to, from, data, value, nonce, chainId, type, maxFeePerGas, maxPriorityFeePerGas, gas), plus the decoded action type, token name, decimals, a simulation status ('ok' or revert warning), estimated gas units, estimated cost in USD, and estimated native token cost. The transaction is ready to be signed by the caller's wallet; private keys are never involved.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "for": {
   "type": "string"
  },
  "since": {
   "type": "string"
  },
  "token": {
   "type": "string"
  },
  "action": {
   "enum": [
    "native_transfer",
    "token_transfer",
    "approve_token"
   ],
   "type": "string"
  },
  "amount": {
   "type": "number"
  },
  "network": {
   "type": "string"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "note": "Unsigned transaction: sign it with your wallet. Vextorium never sees private keys. Check recipient and amount before signing.",
  "token": "USDC",
  "action": "token_transfer",
  "network": "base",
  "decimals": 6,
  "simulation": "ok",
  "transaction": {
   "to": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
   "gas": "0x12742",
   "data": "0xa9059cbb0000000000000000000000009b9b3f22bebd1e3e528c2759a2ca34cd2e0184a100000000000000000000000000000000000000000000000000000000000f4240",
   "from": "0xd8dA6BF26964aF9D7eed9e03E53415D37aA96045",
   "type": "0x2",
   "nonce": "0x46",
   "value": "0x0",
   "chainId": "0x2105",
   "maxFeePerGas": "0xa7d8c0",
   "maxPriorityFeePerGas": "0xf4240"
  },
  "estimated_gas": 62989,
  "estimated_cost_usd": 0.001013,
  "estimated_native_cost": 3.779e-7
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/vextorium-build-evm-transaction-01f9b82f/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.vextorium.com](https://www.zero.xyz/host/api.vextorium.com/llms.txt)