{"uid":"cap_wwFmqON8AgS21f_9i1A8d","slug":"fastpath-bitcoin-mempool-transaction-lookup-b308ab64","name":"FastPath Bitcoin Mempool Transaction Lookup","description":"FastPath translates Ethereum-style JSON-RPC requests into Bitcoin data, fee intelligence, mempool insight, and Core v31 package signals. Paid by x402.","url":"https://api.nativebtc.org/v1/mempool/tx/%7Btxid%7D","method":"GET","headers":{},"bodySchema":{"type":"object","properties":{"properties":{"type":"string"}}},"responseSchema":{"type":"json","example":{"txid":"81c97a6c5b98a1019095de132727cda868694fb5d92534ebb07e475619e38325","vsize":110,"success":true,"feeRateSatVb":2,"bip125Replaceable":true}},"example":null,"exampleRequest":null,"tags":["x402"],"displayCostAmount":"0.001","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":"$0.001/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.001","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.001","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_gcHIhE2NCEI-CXlcFTGND","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.001","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Fetches Bitcoin mempool details for a specific transaction by txid, returning virtual size, fee rate, and RBF replaceability status.","exampleAgentPrompt":"Can you check the mempool status of Bitcoin transaction 81c97a6c5b98a1019095de132727cda868694fb5d92534ebb07e475619e38325 — I want to know its fee rate in sat/vB, virtual size, and whether it can be replaced with RBF?","exampleUseCases":[{"title":"Check if stuck transaction is bumpable","prompt":"My Bitcoin transaction 81c97a6c5b98a1019095de132727cda868694fb5d92534ebb07e475619e38325 hasn't confirmed in hours — can you check the mempool and tell me if it's RBF replaceable so I can try to bump the fee?"},{"title":"Verify fee rate of outgoing payment","prompt":"I just sent a Bitcoin payment with txid 81c97a6c5b98a1019095de132727cda868694fb5d92534ebb07e475619e38325 — what fee rate in sat/vB is it paying and what's the virtual size of the transaction?"},{"title":"Monitor unconfirmed transaction size","prompt":"Can you pull up the mempool details for Bitcoin tx 81c97a6c5b98a1019095de132727cda868694fb5d92534ebb07e475619e38325 and tell me its vsize so I can estimate when it'll get picked up by miners?"}],"resultDescription":"Returns a JSON object with the transaction ID, virtual size in vbytes (vsize), fee rate in satoshis per virtual byte (feeRateSatVb), whether the transaction signals BIP-125 RBF replaceability (bip125Replaceable), and a success boolean indicating whether the transaction was found in the mempool.","failureModes":["Transaction not found in mempool (already confirmed or never broadcast) — success: false","Invalid or malformed txid format — likely 400 or error response","Transaction already confirmed and no longer in mempool","Payment failure via x402 — 402 response if USDC payment not included or insufficient","Network timeout if mempool is under heavy load"],"whenToPreferThis":"Use this endpoint when you need real-time mempool data for a specific Bitcoin transaction — especially fee rate in sat/vB, virtual size, and RBF status. It is ideal for agents that need to decide whether to bump a transaction's fee, verify a payment is in-flight, or programmatically monitor unconfirmed transactions. Prefer this over general block explorer APIs if you need structured JSON output compatible with Ethereum-style tooling or are already using the FastPath/NativeBTC stack.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-09-12T12:30:02.482Z","isFirstParty":false}