{"uid":"cap_hwDJvrAP31pFdgbMbo9cn","slug":"defi-hugen-tokyo-d6dc68d2","name":"EVM Transaction Simulator","description":"Simulate an EVM transaction before execution — preview gas costs, token balance changes, approval modifications, and detect sandwich attacks or unexpected transfers. Supports any EVM chain. Premium endpoint ($0.02). No API keys needed. Accepts USDC payments on Base and Solana","url":"https://defi.hugen.tokyo/defi/simulate","method":"POST","headers":{},"bodySchema":{"properties":{"input":{"required":["method"]}}},"responseSchema":null,"example":{"request":{"to":"0x68b3465833fb72B5A828cCEEad996fc3cA6B0A89","data":"0xa9059cbb0000000000000000000000001234567890123456789012345678901234567890000000000000000000000000000000000000000000000000016345785d8a0000","from":"0x1234567890123456789012345678901234567890","value":"0","chain_id":1,"gas_limit":"100000"},"response":{"logs":[],"flagged":[],"used_gas":0,"is_revert":false,"is_simulated":false,"revert_reason":"","suspicious_url":false,"suspicious_addresses":[],"erc20_balance_changes":[],"erc721_balance_changes":[],"native_balance_changes":[],"simulate_failed_reason":"","erc1155_balance_changes":[],"erc20_allowance_changes":[],"erc721_allowance_changes":[],"erc1155_allowance_changes":[]}},"exampleRequest":{"to":"0x68b3465833fb72B5A828cCEEad996fc3cA6B0A89","data":"0xa9059cbb0000000000000000000000001234567890123456789012345678901234567890000000000000000000000000000000000000000000000000016345785d8a0000","from":"0x1234567890123456789012345678901234567890","value":"0","chain_id":1,"gas_limit":"100000"},"tags":["x402"],"displayCostAmount":"0.02","displayCostAsset":"USDC","priceDynamic":false,"priceHint":null,"priceStatus":"priced","priceSource":"settled","requiresHandshake":false,"reviewCount":0,"rating":{"score":"0.00","successRate":"0.00","reviews":0,"stars":null,"state":"unrated"},"availabilityStatus":"unknown","priceObserved":null,"sessionDeposit":null,"pricing":{"kind":"static","summary":"$0.02/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.02","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.02","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_c_m4BZoudKANNyW0rc2OK","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.02","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Simulates an EVM transaction before execution to preview gas costs, token balance changes, approval modifications, and detect sandwich attacks or unexpected transfers on any EVM chain","exampleAgentPrompt":"Before I sign this transaction, can you simulate it on Ethereum mainnet and show me the expected gas cost, any token balance changes, approval changes, and whether it's vulnerable to a sandwich attack? Here's the raw transaction data: 0x...","exampleUseCases":null,"resultDescription":"Returns a simulation result including estimated gas cost, token balance deltas for all affected addresses, any token approval modifications, detection of sandwich attack vectors, and flags for unexpected or anomalous transfers — all without broadcasting to the network.","failureModes":["Invalid or malformed transaction data returns a parsing error","Unsupported EVM chain ID returns an unsupported chain error","Simulation reverts if the transaction would revert on-chain","Insufficient USDC payment returns a 402 payment required response","Network congestion or node unavailability may cause timeout errors"],"whenToPreferThis":"Use this endpoint when you need to pre-flight any EVM transaction before broadcasting — especially for DeFi interactions involving token swaps, approvals, or bridge calls where gas cost predictability, MEV/sandwich attack risk, and unexpected side effects matter. Prefer this over manual gas estimation tools when you need a full simulation of balance changes, approvals, and security checks in a single call across any EVM-compatible chain.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-09-15T06:30:50.110Z","isFirstParty":false}