{"uid":"cap_hE4hduMZSG1et6HX8uISg","slug":"txsim-decoder-api-evm-simulation-calldata-decoder-dc27eab0","name":"TxSim Decoder API — EVM Simulation & Calldata Decoder","description":"Pay-per-call EVM transaction simulation and calldata decoder for agents: decode raw calldata into a named function with security risk flags, and run a keyless eth_call preview to see whether a transaction would succeed or revert before signing. Across base, ethereum, arbitrum, optimism, polygon, bsc. Deterministic JSON, no RPC keys or node infra needed.","url":"https://simulate.cyberwarex.com/simulate?utm_source=zero.xyz","method":"GET","headers":{},"bodySchema":{"type":"object","$schema":"https://json-schema.org/draft/2020-12/schema","required":["input"],"properties":{"input":{"type":"object","required":["type","method"],"properties":{"type":{"type":"string","const":"http"},"method":{"enum":["GET","HEAD","DELETE"],"type":"string"},"queryParams":{"type":"object","required":["to"],"properties":{"to":{"type":"string","pattern":"^0x[a-fA-F0-9]{40}$","description":"Target contract or account address."},"data":{"type":"string","pattern":"^0x[a-fA-F0-9]*$","description":"Transaction calldata (hex)."},"from":{"type":"string","pattern":"^0x[a-fA-F0-9]{40}$","description":"Sender address for the eth_call preview."},"chain":{"enum":["base","ethereum","arbitrum","optimism","polygon","bsc"],"type":"string","default":"base","description":"EVM chain to simulate on."},"value":{"type":"string","description":"Native value in wei (optional, decimal or 0x hex)."}},"additionalProperties":false}},"additionalProperties":false},"output":{"type":"object","required":["type"],"properties":{"type":{"type":"string"},"example":{"type":"object","properties":{"to":{"type":"string"},"note":{"type":"string"},"risk":{"type":"object","description":"level (none|caution|danger) + flags."},"chain":{"type":"string"},"decoded":{"type":"object","description":"function, signature, args."},"disclaimer":{"type":"string"},"asset_changes":{"type":"null","description":"v2: needs a tracing RPC key."},"revert_reason":{"type":["string","null"]},"would_succeed":{"type":["boolean","null"]}}}}}}},"responseSchema":{"type":"json","example":{"to":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","note":"asset-level change tracing requires a tracing RPC key (v2)","risk":{"flags":[],"level":"none"},"chain":"base","decoded":{"args":{"to":"0xd8dA6BF26964aF9D7eEd9e03E53415D37aA96045","amount":"100000000"},"function":"transfer","signature":"transfer(address,uint256)"},"disclaimer":"Static decode + keyless eth_call preview only. This is not financial advice and not a guarantee: a call that would succeed now can still revert at broadcast time (state changes, slippage, MEV). Always verify before signing.","asset_changes":null,"revert_reason":null,"would_succeed":true}},"example":null,"exampleRequest":null,"tags":["x402"],"displayCostAmount":"0.005","displayCostAsset":"USDC","priceDynamic":false,"priceHint":null,"priceStatus":"priced","priceSource":"probe","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":"$0.005/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.005","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.005","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_L70WULccMkZtql0AmfP97","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.005","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Decodes raw EVM calldata into a named function with security risk flags and runs a keyless eth_call preview to determine if a transaction would succeed or revert before signing.","exampleAgentPrompt":"Before I sign this transaction, can you decode the calldata 0xa9059cbb000000000000000000000000d8da6bf26964af9d7eed9e03e53415d37aa960450000000000000000000000000000000000000000000000000000000005f5e100 targeting contract 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 on Base, tell me what function it calls, flag any security risks, and simulate whether it would succeed?","exampleUseCases":[{"title":"Pre-sign token transfer safety check","prompt":"I'm about to sign a USDC transfer on Base — the target is 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 and the calldata is 0xa9059cbb000000000000000000000000d8da6bf26964af9d7eed9e03e53415d37aa960450000000000000000000000000000000000000000000000000000000005f5e100. Can you decode what it's doing, check for risk flags, and tell me if it would succeed?"},{"title":"DeFi swap revert diagnosis","prompt":"My swap transaction on Arbitrum keeps failing — the contract is 0x1b02dA8Cb0d097eB8D57A175b88c7D8b47997506 and my calldata is 0x38ed1739... from address 0xAbCd1234...5678. Can you simulate it and tell me the revert reason so I know why it's not going through?"},{"title":"Suspicious calldata security audit","prompt":"Someone sent me a transaction to sign on Ethereum targeting 0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D with calldata 0x095ea7b3... — can you decode exactly what function this is calling and flag any danger or security risks before I approve it?"}],"resultDescription":"A JSON object containing: the decoded function name, signature, and named arguments; a risk assessment with a level (none, caution, or danger) and specific flags; a would_succeed boolean indicating if the eth_call simulation passed; a revert_reason string if it failed; asset_changes (v2, requires tracing RPC); and contextual notes and disclaimers about simulation limitations.","failureModes":["Invalid or malformed 'to' address returns a validation error","Unsupported chain name returns an enum validation error","Malformed or unrecognized calldata hex may result in an undecoded response with null decoded fields","Network or RPC issues for the target chain may cause simulation failures","Transactions that depend on real-time state (e.g. slippage-sensitive swaps) may show would_succeed=true but revert at broadcast time","Missing 'to' parameter (required) returns a schema validation error"],"whenToPreferThis":"Choose this endpoint when you need a keyless, infrastructure-free way to decode raw EVM calldata and/or simulate a transaction across Base, Ethereum, Arbitrum, Optimism, Polygon, or BSC before signing. Ideal for agents performing pre-sign safety checks without managing RPC nodes or API keys. Prefer this over full tracing RPCs for lightweight decode+simulate needs; use a tracing RPC for full asset-change tracking (v2 feature).","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-10-02T02:43:59.396Z","isFirstParty":false,"canonicalSlug":"txsim-decoder-api-evm-simulation-calldata-decoder-dc27eab0"}