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Nishvault x402 Pre-Send Guard
x402
Nishvault x402 Pre-Send Guard is a paid API for AI agents from x402-discovery.nishvault.com, paid per call via x402, $0.01/call, status unknown (last checked 2026-09-13).
Returns an x402 v2 payment challenge for a Base-mainnet EVM transaction preflight simulation before any transaction is broadcast.
Price / call$0.01
Success—
StatusUnknown
How this service works
Machine-readable discovery for the paid Base-mainnet transaction preflight. The endpoint returns an x402 v2 payment challenge before any transaction is broadcast.
Output
The endpoint returns an x402 v2 payment challenge response. Upon payment of $0.01 USDC, the caller receives the preflight simulation result indicating whether the given EVM transaction (to, from, data, optional value, optional chainId) would succeed or fail on Base mainnet before any actual broadcast occurs.
Example use cases
Safe token transfer preflight
“Simulate this ERC-20 transfer on Base before I send it — from 0xSender...abc to 0xRecipient...def with calldata 0xa9059cbb... and a value of 0x0 — I want to make sure it won't revert.”
DeFi swap dry-run check
“Can you preflight this DEX swap calldata on Base mainnet for me? Sender is 0xMyWallet...111, contract is 0xUniswap...222, and the hex calldata is 0x38ed1739... — I need to know it's safe before I broadcast.”
NFT mint transaction validation
“Before I mint this NFT on Base, run a preflight simulation — from address 0xMinter...aaa, to the NFT contract 0xCollection...bbb, with calldata 0x1249c58b and value 0x16345785d8a0000.”
Technical details
Endpoint
POSThttps://x402-discovery.nishvault.com/simulate/transaction-preflightWhen to prefer
Choose this endpoint when you need to preflight or dry-run an EVM transaction specifically on Base mainnet before broadcasting it, particularly when using the x402 micropayment protocol for per-call billing. It is ideal for agents that must avoid costly failed transactions and want a machine-readable simulation check at minimal cost ($0.01 USDC).
Side effects
- Missing required fields (to, from, data) returns a 400 or validation error
- Invalid hex calldata or malformed EVM addresses cause rejection
- Payment challenge not fulfilled results in 402 response without simulation data
- Unsupported chainId (non-Base mainnet) may cause simulation failure
- Network or RPC errors on the Base mainnet node can return 5xx responses
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| torequired | string | EVM destination address used for simulation. |
| datarequired | string | Hexadecimal EVM calldata. |
| fromrequired | string | EVM sender address used for simulation. |
| value | string | Optional hexadecimal wei value. |
| chainId | string | Base mainnet chain ID in hexadecimal. |
Tags
x402
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