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Transaction Simulation (Base Chain Pre-execution Check)
x402
Transaction Simulation (Base Chain Pre-execution Check) is a paid API for AI agents from 402.com.tr, paid per call via x402, $0.03/call, status unknown (last checked 2026-10-12).
Simulates an unsigned Ethereum transaction against live Base chain state, returning success/revert status, revert reason, gas estimate, ETH cost, and decoded approval risk flags (unlimited approvals, setApprovalForAll) before signing.
Price / call$0.03
Success—
StatusUnknown
How this service works
Simulate an UNSIGNED transaction against live Base state before an agent signs: will it SUCCEED or revert (with the contract's own reason), the gas estimate and ETH cost, and — decoded from the calldata — whether it grants an approval, and whether that approval is UNLIMITED (approve/permit) or a setApprovalForAll, the classic drain vectors. Pass from, to, and optionally data (calldata) + value. The pre-execution check the agent-safety playbook says to run and block on. Not financial advice.
Output
Returns whether the transaction would succeed or revert (with the contract's own revert reason string), a gas estimate and ETH cost, and decoded calldata flags indicating whether the transaction grants a token approval, whether that approval is unlimited (approve/permit style), and whether it uses setApprovalForAll — the classic NFT/ERC20 drain vectors.
Example use cases
DeFi approval safety check before signing
“I'm about to approve a DeFi contract on Base — sender is 0x1234...abcd, contract is 0x5678...ef01, calldata is 0x095ea7b3... — can you simulate this transaction and tell me if it's granting an unlimited approval before I sign anything?”
Pre-flight revert check for DEX swap
“Simulate this Base swap transaction for me before I submit it: from 0xaaaa...1111 to the Uniswap router at 0xbbbb...2222, with this calldata 0x5ae4...8fa3 and 0.05 ETH value — will it succeed or revert, and what's the gas cost?”
Agent safety gate for wallet automation
“My automated agent is about to send a transaction on Base from 0xcccc...3333 to 0xdddd...4444 with calldata 0x23b8...9ab2 — run a pre-execution simulation and block it if it reverts or if the calldata looks like a setApprovalForAll drain.”
Technical details
Endpoint
GEThttps://402.com.tr/api/x402/simulate-tx?utm_source=zero.xyzWhen to prefer
Use this endpoint when an AI agent or wallet interface needs a safety gate before prompting a user to sign any Base chain transaction — especially when the calldata involves token approvals, DeFi interactions, or unfamiliar contracts. Prefer this over generic gas estimators when you need approval-type decoding and drain-vector detection in a single call. Ideal for agent-safety playbooks where blocking on revert or unlimited approvals is required before execution.
Side effects
- Missing required 'from' or 'to' parameters — returns 400 error
- Invalid or malformed Ethereum address — returns error response
- Malformed calldata hex — may fail to decode or simulate correctly
- Base RPC node unavailable — simulation cannot be completed
- Transaction simulation gas exceeds block limit — revert with out-of-gas
- Network congestion may cause stale state snapshots
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Tags
x402
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