Vextorium Build EVM Transaction

x402

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.

Price / call$0.004

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StatusUnknown

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.

Example use cases

Safe USDC transfer before signing

“I want to send 50 USDC to 0x9b9b3f22bebd1e3e528c2759a2ca34cd2e0184a1 on Base from my wallet 0xd8dA6BF26964aF9D7eed9e03E53415D37aA96045 — can you build the unsigned transaction and tell me if it'll succeed and what the gas cost will be?”

ERC-20 approve for DeFi protocol

“Prepare an unsigned token_transfer approve transaction for 1000 USDC on Base from 0xd8dA6BF26964aF9D7eed9e03E53415D37aA96045 to the Uniswap router at 0x3fC91A3afd70395Cd496C647d5a6CC9D4B2b7FAD — show me the nonce, chainId, and estimated fee in USD before I sign anything.”

Native ETH transfer transaction prep

“Build a raw unsigned transaction to send 0.05 ETH from 0xd8dA6BF26964aF9D7eed9e03E53415D37aA96045 to 0xAbCd1234567890abcdef1234567890abcdef1234 on Ethereum mainnet — I need the full transaction object with EIP-1559 fees and a simulation to confirm it won't revert.”

Technical details

Endpoint

POSThttps://api.vextorium.com/v1/build-transaction?utm_source=zero.xyz

When to prefer

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.

Side effects

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

Input

Schema · Request body

Field	Type	Description
for	string
since	string
token	string
action	string
amount	number
network	string

Output

Schema · Response

{
  "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
  }
}

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