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Base Transaction Simulator (tx-simulate)
x402
Base Transaction Simulator (tx-simulate) is a paid API for AI agents from kr-x402-mvp.kgy5612.workers.dev, paid per call via x402, $0.003/call, status unknown (last checked 2026-10-31).
Simulates one or more Base chain transactions before sending, returning success/failure verdict, gas cost, token transfers, approval events, and balance changes.
Price / call$0.003
Success—
StatusUnknown
How this service works
Pay-per-call crypto microdata for trading/onchain AI agents via x402 (USDC on Base): Base gas, token risk, balances, multi-venue prices, Hyperliquid book/funding, kimchi premium. No API keys.
Output
Returns a JSON object with: overall success boolean, a SAFE_TO_SEND/REVERT verdict string, total gas used, fee in ETH and USD, a list of per-call results (success, function signature, gas used, revert reason if any), decoded token transfers with amounts and symbols, approval events, net balance changes per address per token, flags for anomalies, and links to related endpoints for next steps.
Example use cases
Pre-flight check before DeFi swap
“I'm about to execute a swap on Base — sender is 0xe4be4d0bd82d8e68203deff81f79ede0529f2617, going to 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 with this calldata. Simulate it first and tell me if it's safe to send, what the gas cost will be in USD, and what my balance will look like after.”
Detect malicious contract before signing
“Someone sent me a transaction to sign on Base — to address 0x1234abcd... with some calldata. Can you simulate it and tell me the verdict: is it SAFE_TO_SEND? And show me every token approval and transfer it would trigger so I can verify nothing suspicious is happening.”
Simulate chained multicall on Base
“I want to run two contract calls back-to-back from my wallet 0xe4be4d0bd82d8e68203deff81f79ede0529f2617 on Base — first approve USDC, then swap. Simulate both as a sequence and tell me if they both succeed, what the total gas cost is, and what my final balances will be.”
Technical details
Endpoint
GEThttps://kr-x402-mvp.kgy5612.workers.dev/api/tx-simulate?utm_source=zero.xyzWhen to prefer
Use this endpoint when an AI agent needs to pre-flight a Base transaction before submitting it — especially for DeFi interactions, token transfers, or any calldata the agent hasn't verified. It is uniquely suited for detecting reverts, decoding what a transaction actually does, previewing balance changes, and flagging suspicious approvals — all without spending gas. Choose it over a generic gas estimator when you need the full decoded picture of a transaction's effects, not just a gas number.
Side effects
- Invalid address format returns 400 validation error
- Malformed calldata (odd-length hex) rejected at input validation
- Sender with zero ETH/token balance may simulate a revert if the contract checks balances
- Network timeout if Base RPC is congested
- More than 5 calls in the multicall array rejected
- Block state may be 1-2 blocks stale leading to minor gas estimation drift
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Output
Schema · Response
{
"type": "json",
"example": {
"from": "0xe4be4d0bd82d8e68203deff81f79ede0529f2617",
"next": [
"/crypto/base-gas",
"/crypto/tx-status?hash="
],
"block": 53272234,
"calls": [
{
"to": "0x833589fcd6edb6e08f4c7c32d4f71b54bda02913",
"index": 0,
"success": true,
"function": "transfer(address,uint256)",
"gas_used": 45047,
"revert_reason": null
}
],
"chain": "base",
"flags": [],
"fee_eth": 5e-7,
"fee_usd": 0.0019,
"success": true,
"summary": "1 call succeeds; sender sends 0.001 USDC",
"verdict": "SAFE_TO_SEND",
"approvals": [],
"transfers": [
{
"to": "0xa587d73489f8f09d1975f1ddbb1c61c93e8fa9d7",
"from": "0xe4be4d0bd82d8e68203deff81f79ede0529f2617",
"token": "0x833589fcd6edb6e08f4c7c32d4f71b54bda02913",
"amount": 0.001,
"symbol": "USDC"
}
],
"gas_used_total": 45047,
"sender_changes": {
"USDC": -0.001
},
"balance_changes": {
"0xa587d73489f8f09d1975f1ddbb1c61c93e8fa9d7": {
"USDC": 0.001
},
"0xe4be4d0bd82d8e68203deff81f79ede0529f2617": {
"USDC": -0.001
}
}
}
}Tags
x402
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