{"uid":"cap_VsLrn6FGdywFj1i3kK5F9","slug":"avasis-base-transaction-pre-check-208f09a4","name":"Avasis Base Transaction Pre-Check","description":"Pre-sign tx precheck for Base (chain 8453, $0.02): simulate transaction {from,to,data,value} with eth_simulateV1 before signing. Returns would_revert + reason, gas USD, each ETH/ERC-20/NFT transfer with USD, wallet PnL (net_for_from usd_net), approval risk (spender, unlimited:true, USD exposure), counterparty risk (GoPlus + OFAC), decoded method, SIGN/CAUTION/BLOCK verdict with reasons. POST JSON or GET. Free live sample /v1/evm/tx-precheck/sample. Advice only; RPC down 502, never charged.","url":"https://agents.avasis.ai/v1/base/tx-precheck?utm_source=zero.xyz","method":"GET","headers":{},"bodySchema":{"type":"object","$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"},"queryParams":{"type":"object","required":["from","to"],"properties":{"to":{"type":"string","description":"the transaction's to (contract or recipient, 0x + 40 hex)"},"gas":{"type":"integer","maximum":30000000,"minimum":21000,"description":"optional gas limit for the cost columns (default: the simulation's gas_used)"},"data":{"type":"string","description":"calldata as 0x hex (omit or 0x for a plain ETH transfer); max 6 KB"},"from":{"type":"string","description":"the signer's wallet (0x + 40 hex): the account that would sign; its ETH balance, allowances granted and net position are checked"},"chain":{"type":"string","description":"optional; must be base / 8453 on this route"},"value":{"type":"string","description":"ETH value in wei as a decimal or 0x hex integer string (default 0)"}},"additionalProperties":false}},"additionalProperties":false},"output":{"type":"object","required":["type"],"properties":{"type":{"type":"string"},"example":{"type":"object","required":["chain","verdict","decoded","sim","transfers","net_for_from","approvals","risk"],"properties":{"tx":{"type":"object"},"sim":{"type":"object"},"risk":{"type":"object"},"chain":{"type":"string"},"signer":{"type":"object"},"decoded":{"type":"object"},"verdict":{"type":"object"},"chain_id":{"type":"integer"},"precheck":{"type":"string"},"approvals":{"type":"array"},"transfers":{"type":"array"},"disclaimer":{"type":"string"},"net_for_from":{"type":"object"},"also_available":{"type":"object"}}}}}}},"responseSchema":{"type":"json","example":{"tx":{"to":"0x833589fcd6edb6e08f4c7c32d4f71b54bda02913","data":"0x095ea7b30000000000000000000000002626664c2603336e57b271c5c0b26f421741e481ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff","from":"0xf977814e90da44bfa03b6295a0616a897441acec","gas_limit":null,"value_eth":"0","value_wei":"0","data_bytes":68},"sim":{"rpc":"base-rpc.publicnode.com","method":"eth_simulateV1 (traceTransfers, validation off; funds checked separately)","status":"0x1","eth_usd":2580.5,"gas_usd":0.000865,"chain_id":8453,"gas_used":55785,"block_tag":"latest","gas_price":{"basis":"effective = base fee + priority (standard tier); max = 2 x base fee + priority","max_fee_wei":"11000000","base_fee_wei":"5000000","priority_wei":"1000000","effective_wei":"6000000"},"gas_usd_max":0.001585,"return_data":"0x0000000000000000000000000000000000000000000000000000000000000001","block_number":53394126,"gas_cost_eth":"0.00000033471","would_revert":false,"revert_reason":null,"eth_usd_source":"chainlink ETH/USD (latestRoundData)","block_timestamp":1793180287,"l1_data_fee_eth":"0.000000000488126494","gas_limit_used_for_cost":55785},"risk":{"ofac":{"hits":[],"available":true},"flags":[{"code":"UNLIMITED_APPROVAL","label":"an unlimited allowance: the spender can move your whole balance of that token at any later time","level":"CAUTION","evidence":"Uniswap SwapRouter02 on USDC: $1234.56 of your balance exposed now"}],"goplus":{"source":"GoPlus address_security (keyless)","screened":2,"unavailable":0},"counterparties":[{"ofac":false,"role":"to","known":"USDC (Circle)","goplus":{"warn":[],"block":[],"available":true},"address":"0x833589fcd6edb6e08f4c7c32d4f71b54bda02913","is_contract":false}]},"chain":"base","signer":{"nonce":1200,"address":"0xf977814e90da44bfa03b6295a0616a897441acec","funds_ok":true,"balance_eth":"2.5","needs_eth_max":"0.000000614123126494"},"decoded":{"args":{"amount_raw":"115792089237316195423570985008687907853269984665640564039457584007913129639935","spender_or_to":"0x2626664c2603336e57b271c5c0b26f421741e481"},"kind":"approve","method":"approve","selector":"0x095ea7b3","to_known":"USDC (Circle)","one_liner":"approve: let Uniswap SwapRouter02 spend UNLIMITED USDC from your wallet","signature":"approve(address,uint256)"},"verdict":{"level":"CAUTION","action":"sign only after reviewing the reasons","reasons":["UNLIMITED_APPROVAL: Uniswap SwapRouter02 on USDC: $1234.56 of your balance exposed now"],"headline":"CAUTION: approve: let Uniswap SwapRouter02 spend UNLIMITED USDC from your wallet"},"chain_id":8453,"precheck":"evm-tx-precheck-1","approvals":[{"nft":false,"owner":"0xf977814e90da44bfa03b6295a0616a897441acec","token":"0x833589fcd6edb6e08f4c7c32d4f71b54bda02913","amount":"unlimited","symbol":"USDC","spender":"0x2626664c2603336e57b271c5c0b26f421741e481","by_signer":true,"unlimited":true,"amount_raw":"115792089237316195423570985008687907853269984665640564039457584007913129639935","token_known":"USDC (Circle)","usd_exposure":1234.56,"spender_known":"Uniswap SwapRouter02","exposure_basis":"your whole current balance of this token (allowance covers it)","signer_balance":"1234.56","covers_full_balance":true,"spender_is_contract":true}],"transfers":[],"disclaimer":"advice only; see the paid body","net_for_from":{"note":"usd_net = ETH delta - gas + priced token deltas, at current prices","tokens":[],"usd_net":-0.000865,"unpriced":[],"eth_delta":"0","gas_cost_eth":"0.000000335198126494","gas_cost_usd":0.000865,"gas_cost_wei":"335198126494","eth_delta_usd":0,"eth_delta_wei":"0","usd_net_complete":true,"eth_delta_after_gas":"-0.000000335198126494"},"also_available":{"how":"same x402 flow as this quote (USDC on Base, no account or API key); an unpaid GET on any url is a free quote; free samples at /v1/evm/<sku>/sample","items":[{"url":"https://agents.avasis.ai/v1/base/tx-receipt","what":"Base tx receipt + status: after you send, wait for the receipt (up to 30 s), decoded transfers, fee in USD, revert reason, or a pending/stuck diagnosis","price_usd":"0.02","free_sample":"https://agents.avasis.ai/v1/evm/tx-receipt/sample"},{"url":"https://agents.avasis.ai/v1/base/erc20-allowance","what":"Base ERC-20 allowance check: is the spender approved, for how much, does the owner hold it; ready approve / revoke calldata","price_usd":"0.02","free_sample":"https://agents.avasis.ai/v1/evm/erc20-allowance/sample"}],"ladder":"$0.02 Base tx precheck (this call) -> $0.02 Base tx-receipt https://agents.avasis.ai/v1/base/tx-receipt (after you send) -> $0.02 Base erc20-allowance https://agents.avasis.ai/v1/base/erc20-allowance | $0.02 Base multi-balance https://agents.avasis.ai/v1/base/multi-balance; free samples https://agents.avasis.ai/v1/evm/{tx-precheck,tx-receipt,erc20-allowance,multi-balance}/sample"}}},"example":null,"exampleRequest":null,"tags":["x402"],"displayCostAmount":"0.02","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":"$0.02/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_OYOfvigBfk9Mr8Hkhfnje","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 Ethereum Base chain transaction before signing, returning revert risk, gas cost in USD, token transfers with USD values, approval risks, counterparty risk scores, and a SIGN/CAUTION/BLOCK verdict.","exampleAgentPrompt":"Before I sign this transaction, can you simulate it on Base and tell me whether it'll revert, how much gas it'll cost in USD, what tokens will move, and whether I should sign it or block it? From wallet 0xYourWallet, to 0xContractAddress, with calldata 0xabcdef and 0 ETH value.","exampleUseCases":[{"title":"DeFi swap safety check before signing","prompt":"I'm about to approve a Uniswap swap on Base — from my wallet 0xABC123, to contract 0xDEF456, with calldata 0x38ed1739... and 0 ETH value. Can you simulate it and tell me if it'll revert, what tokens I'll lose or gain in USD, and whether the approval looks safe?"},{"title":"Unlimited ERC-20 approval risk detection","prompt":"This dApp wants me to sign an approve transaction on Base from 0xMYWALLET to spender 0xSPENDER with calldata 0x095ea7b3... — can you check if it's asking for unlimited token approval, estimate my USD exposure, and give me a SIGN or BLOCK recommendation?"},{"title":"NFT transfer counterparty OFAC check","prompt":"I'm sending an NFT on Base from 0xSENDER to 0xRECIPIENT with calldata 0xa9059cbb... — run a pre-check and tell me if the recipient is on any OFAC blocklist or flagged by GoPlus, what the net transfer looks like in USD, and whether I'm safe to proceed."}],"resultDescription":"A JSON object containing: chain identifier, simulation result (would_revert, revert reason), decoded method name and parameters, list of ETH/ERC-20/NFT transfers each with USD value, wallet net PnL (net_for_from with usd_net), array of approval risks (spender address, unlimited flag, USD exposure), counterparty risk scores from GoPlus and OFAC check, estimated gas cost in USD, and a final verdict object with SIGN / CAUTION / BLOCK decision plus human-readable reasons.","failureModes":["502 Bad Gateway if the Base RPC node is down — no charge is applied","Missing required 'from' or 'to' query parameters returns a 400 validation error","Invalid hex format for 'data' or 'from'/'to' addresses returns a schema validation error","Calldata exceeding 6 KB is rejected","Simulation may return would_revert:true with a revert reason if the transaction would fail on-chain","If GoPlus or OFAC services are unavailable, counterparty risk fields may be null or incomplete"],"whenToPreferThis":"Use this endpoint when an AI agent or wallet interface needs to validate a Base chain (chain 8453) transaction before the user signs it — especially when you need USD-denominated cost/transfer previews, approval risk scoring, GoPlus+OFAC counterparty checks, and a single SIGN/CAUTION/BLOCK verdict in one call. Prefer it over raw eth_simulateV1 calls when you want pre-parsed, human-readable risk output rather than raw simulation data. It is specifically scoped to Base; use sibling endpoints for Ethereum mainnet or Solana.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-11-01T06:30:32.889Z","isFirstParty":false,"canonicalSlug":"avasis-base-transaction-pre-check-208f09a4"}