{"uid":"cap_S7nzAxsjWk0ApBKvqdyab","slug":"preflight-bitcoin-transaction-input-context-16d34a7a","name":"Preflight Bitcoin Transaction Input Context","description":"Call before signing a Bitcoin transaction when you need chain context for its inputs: whether each prevout exists, whether it is already spent, its value in sats and its confirmations. Resolves up to 10 inputs against a public explorer at about one request per second, so a full batch can take over 20 seconds; figures reflect chain state at checked_at. Describes on-chain facts with source links; never advises whether to sign.","url":"https://preflight402.com/v1/btc/tx-context?utm_source=zero.xyz","method":"POST","headers":{},"bodySchema":{"type":"object","properties":{"inputs":{"type":"array","items":{"type":"object","required":["txid","vout"],"properties":{"txid":{"type":"string","pattern":"^[0-9a-f]{64}$"},"vout":{"type":"integer","maximum":100000,"minimum":0}},"additionalProperties":false},"maxItems":10,"minItems":1},"network":{"enum":["mainnet","testnet"],"type":"string","default":"mainnet"}}},"responseSchema":null,"example":null,"exampleRequest":null,"tags":["x402"],"displayCostAmount":"0.1","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":"$0.1/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.1","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.1","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_UXa2FTh8MiQmxg7JpZl4f","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.1","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Looks up chain context for Bitcoin transaction inputs — checking if each prevout exists, is spent, its value in satoshis, and its confirmation count — before signing.","exampleAgentPrompt":"Before I sign this Bitcoin transaction, check the chain context for these two inputs on mainnet: txid a3f1...bc12 vout 0, and txid 9e44...7f01 vout 2 — are they unspent, what are their values in sats, and how many confirmations do they have?","exampleUseCases":[{"title":"PSBT signing safety check","prompt":"I'm about to sign a PSBT with 3 inputs on mainnet — txid 1a2b...cd34 vout 0, txid 5e6f...ab78 vout 1, and txid 9c0d...ef12 vout 2. Can you verify all three prevouts exist on-chain, aren't already spent, and tell me their sat values and confirmation counts?"},{"title":"Double-spend detection before broadcast","prompt":"Before I broadcast this Bitcoin transaction, check whether the input at txid b7e3...44fa vout 0 on mainnet is still unspent — I want to make sure nobody else has spent it already."},{"title":"UTXO value confirmation for fee estimation","prompt":"I need to know the exact satoshi values and confirmation counts for these Bitcoin outputs on mainnet so I can estimate fees accurately: txid c1d2...3e4f vout 1 and txid a9b8...7c6d vout 0."}],"resultDescription":"Returns per-input chain facts: whether each prevout exists on-chain, whether it is already spent, its value in satoshis, and its confirmation count, along with a checked_at timestamp and source explorer links. Covers up to 10 inputs per call; results reflect chain state at the moment of the check.","failureModes":["Invalid txid format (not 64 lowercase hex characters) returns a validation error","vout index out of range (above 100000) is rejected","Prevout not found on the specified network returns a not-found status rather than an error","Rate limiting from the underlying public explorer may cause timeouts for full 10-input batches (>20 seconds)","Network mismatch (checking testnet txid against mainnet) returns not-found","More than 10 inputs in a single request is rejected"],"whenToPreferThis":"Use this endpoint when an AI agent or wallet needs to verify Bitcoin UTXO chain state before signing a transaction — specifically when you need existence, spent status, satoshi value, and confirmations for up to 10 inputs in one call. Prefer this over manual explorer queries when you want structured, machine-readable results with source attribution. Note it only advises on on-chain facts and never recommends whether to sign.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-10-02T00:43:21.948Z","isFirstParty":false,"canonicalSlug":"preflight-bitcoin-transaction-input-context-16d34a7a"}