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Preflight Bitcoin Transaction Input Context
x402
Preflight Bitcoin Transaction Input Context is a paid API for AI agents from preflight402.com, paid per call via x402, $0.1/call, status unknown (last checked 2026-10-02).
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.
Price / call$0.1
Success—
StatusUnknown
How this service works
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.
Output
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.
Example use cases
PSBT signing safety check
“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?”
Double-spend detection before broadcast
“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.”
UTXO value confirmation for fee estimation
“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.”
Technical details
Endpoint
POSThttps://preflight402.com/v1/btc/tx-context?utm_source=zero.xyzWhen to prefer
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.
Side effects
- 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
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputs | array | |
| network | string |
Tags
x402
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