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HALOWERK kettenwerk Transaction Simulator
x402
HALOWERK kettenwerk Transaction Simulator is a paid API for AI agents from kette.halowerk.com, paid per call via x402, $0.012/call, status unknown (last checked 2026-09-15).
Simulates an EVM transaction against a named block state without broadcasting to the chain, measuring exact balance changes for all touched assets including native currency
Price / call$0.012
Success—
StatusUnknown
How this service works
Answers the question that stands before every signature: what really happens to my assets and my rights. The call is executed against the state of a named block on a simulation interface, never on the chain — this hub holds no private key and broadcasts nothing. Balance changes are not inferred from events but measured: the same simulation reads every touched balance immediately before and immediately after the call, native currency included, so an outflow that emits no event is still visible. A
Output
Returns the net balance changes for every address touched by the simulated call, measured by reading balances immediately before and after execution on the specified block — including native currency (ETH/BNB/MATIC) flows that emit no events, plus any ERC-20 or other token deltas. No transaction is broadcast; no private key is required.
Example use cases
DeFi swap balance audit
“I'm about to call a Uniswap router on Ethereum from 0xMyWallet to 0xRouterAddress with this calldata 0x38ed1739... and 0 ETH. Simulate it against the latest block and tell me exactly how much of each token I gain or lose, including any hidden ETH outflow.”
Pre-signing rug-pull check
“Before I approve this NFT mint transaction on Polygon — from 0xMeAddr to 0xMintContract, data 0x1249c58b, value 50000000000000000 wei — can you simulate it and show me every balance that changes? I want to know if anything drains my wallet unexpectedly.”
Smart contract state override test
“Simulate a call on Arbitrum from 0xTestSender to 0xVaultContract with calldata 0x2e1a7d4d and override the sender's ETH balance to 10 ETH in the state, then tell me what the net balance changes are across all touched addresses.”
Technical details
Endpoint
POSThttps://kette.halowerk.com/tx/simulateWhen to prefer
Choose this endpoint when you need precise balance change accounting for an EVM transaction before signing — especially when the transaction may move assets through paths that emit no Transfer events. It is preferable over event-log parsing when hidden native currency outflows are a concern, and over manual trace analysis when you need a clean before/after balance diff across all touched addresses. Supports Ethereum, Base, Arbitrum, Optimism, Polygon, and BSC with optional state overrides for hypothetical scenario testing.
Side effects
- Invalid address format (must be 0x-prefixed 40-char hex) returns validation error
- Gas limit below 21000 or above 30000000 is rejected
- Unsupported chain name returns enum validation error
- Invalid or non-existent block number causes simulation failure
- Malformed calldata (not 0x-prefixed hex) rejected
- Simulation reverts if the underlying call would revert on-chain
- State override format mismatch with eth_simulateV1 spec causes error
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| to | string | Target address. |
| gas | integer | Optional gas limit for the simulation. |
| data | string | Call data. |
| from | string | Sender address. No signature is needed and none is created. |
| block | string | "latest" or a block number as decimal string. |
| chain | string | Chain to simulate on. |
| value | string | Value in wei, decimal or 0x. |
| state_overrides | object | Optional state overrides per address, in the eth_simulateV1 format (balance, nonce, code, state, stateDiff). |
Tags
x402
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