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Vextorium EVM Transaction Builder
x402
Vextorium EVM Transaction Builder is a paid API for AI agents from api.vextorium.com, paid per call via x402, $0.004/call, status unknown (last checked 2026-10-29).
Builds an unsigned EVM transaction payload (native transfer, ERC-20 transfer, or ERC-20 approve) with full EIP-1559 fee estimates, gas, nonce, and chain ID — ready to sign.
Price / call$0.004
Success—
StatusUnknown
How this service works
Build an EVM transaction ready to sign (never signed or sent): native transfer, ERC-20 transfer or ERC-20 approve, with to, data, value, nonce, chainId, estimated gas and current EIP-1559 fees, plus a simulation that warns if it would revert and the estimated cost.
Output
Returns a fully formed unsigned transaction object containing: to, from, data (calldata), value (in hex), nonce, chainId, type, maxFeePerGas, maxPriorityFeePerGas, and gas (all hex-encoded), along with estimated gas units, estimated cost in USD, estimated cost in native token, token info (address, decimals), action type, network identifier, and an optional simulation note.
Example use cases
Prepare native ETH transfer on Arbitrum
“Build me a raw unsigned transaction to send 0.1 ETH from 0x1111...AAAA to 0x2222...BBBB on Arbitrum — I need the nonce, gas, and current EIP-1559 fees so I can sign it on my side.”
ERC-20 token approval for DeFi protocol
“I need to approve the Uniswap router at 0xRouter...XYZ to spend 1000 USDC from my wallet 0xMyWallet...123 on Ethereum mainnet — can you build the unsigned approve transaction with current gas fees?”
Automated payment pipeline transaction prep
“Prepare an unsigned ERC-20 transfer transaction to move 200 DAI from 0xSender...AAA to 0xReceiver...BBB on Polygon — I need the full transaction object including calldata, nonce, chainId, and estimated cost in USD so my signing service can process it.”
Technical details
Endpoint
POSThttps://api.vextorium.com/construir-transaccion-pago?utm_source=zero.xyzWhen to prefer
Choose this endpoint when you need to construct an EVM transaction for signing externally — ideal for wallets, signing services, or agents that manage their own private keys and need accurate EIP-1559 fee data baked in. Prefer this over on-chain submission services when you want to inspect, modify, or batch-sign transactions before broadcasting. Best suited for native transfers and ERC-20 transfers/approvals on supported EVM chains without needing to implement RPC calls yourself.
Side effects
- Invalid or missing wallet address (desde/para) returns validation error
- Unsupported network identifier returns error indicating chain not found
- Zero or negative amount fails input validation
- Token address missing for transferencia_token or aprobar_token actions
- RPC timeout on target chain causes gas estimation failure
- Token contract not found on specified network
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| red | string | |
| para | string | |
| desde | string | |
| token | string | |
| accion | string | |
| cantidad | number |
Tags
x402
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