{"uid":"cap_51qvrNTY-XTznDYLMYqTr","slug":"transaction-simulation-base-chain-pre-execution-check-c219406d","name":"Transaction Simulation (Base Chain Pre-execution Check)","description":"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.","url":"https://402.com.tr/api/x402/simulate-tx?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"],"type":"string"},"pathParams":{"type":"object"},"queryParams":{"type":"object","required":["from","to"],"properties":{"to":{"type":"string","description":"To (recipient/contract)"},"data":{"type":"string","description":"Calldata (hex, optional)"},"from":{"type":"string","description":"Sender address"},"value":{"type":"string","description":"ETH value (optional)"}}}},"additionalProperties":false},"output":{"type":"object","required":["type"],"properties":{"type":{"type":"string"},"example":{"type":"object"}}}}},"responseSchema":null,"example":null,"exampleRequest":null,"tags":["x402"],"displayCostAmount":"0.03","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":"$0.03/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.03","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.03","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_3aIzM-d3Ma_xZRK0LaRuW","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.03","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"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.","exampleAgentPrompt":"Before I sign this transaction, simulate it against live Base state to check if it will succeed or revert — the sender is 0xAbC...123, the contract is 0xDeF...456, and the calldata is 0xa9059cbb... — and flag any unlimited token approvals or setApprovalForAll patterns in the data.","exampleUseCases":[{"title":"DeFi approval safety check before signing","prompt":"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?"},{"title":"Pre-flight revert check for DEX swap","prompt":"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?"},{"title":"Agent safety gate for wallet automation","prompt":"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."}],"resultDescription":"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.","failureModes":["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"],"whenToPreferThis":"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.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-10-12T18:47:23.388Z","isFirstParty":false,"canonicalSlug":"transaction-simulation-base-chain-pre-execution-check-c219406d"}