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POST
Build UNSIGNED transaction(s) to fund a leg — sign with your own key/HSM, then broadcast

Authorizations

Authorization
string
header
required

An API key (hk_live_… / hk_test_…) with read/taker/maker scopes. read is read-only: every write except webhooks needs taker or maker (403 otherwise), and either of those can read too. Creating RFQs and listing tokens need taker; quoting needs maker.

Path Parameters

id
string
required
leg
enum<string>
required
Available options:
a,
b

Response

chain-specific signing material (EVM txs / BTC pay-to / TRON txs / Solana transaction, base64)

What to sign, per chain family; sign says which shape it is. evm-tx: sign and send each of txs in order, from from when given. btc-payment (fund): pay amountSats to payTo (and feeAmountSats to feePayTo when present). btc-sighash (claim/refund): sign each of sighashHexes, then broadcast { psbtBase64, signaturesHex, preimageHex? }. solana-tx: sign transactionBase64 and broadcast it. tron-txid: sign each transactions[].txID and broadcast each signed transaction.

chain
string
required
family
enum<string>
required
Available options:
evm,
bitcoin,
svm,
tvm
sign
enum<string>
required
Available options:
evm-tx,
btc-payment,
btc-sighash,
solana-tx,
tron-txid
note
string

what to do with it, in words

chainId
integer

evm-tx

from
string

evm-tx (fund) and tron-txid: the address that must sign

txs
object[]

evm-tx: unsigned transactions (an ERC-20 fund is approve, then createSwap)

payTo
string

btc-payment: the escrow (P2WSH) address

amountSats

btc-payment: sats still due to the escrow (string); btc-sighash: what the spend pays out after the network fee (integer)

topUp
boolean

btc-payment: the escrow already holds part of the amount

feePayTo
string

btc-payment: the protocol fee treasury, when this leg carries the fee

feeAmountSats
string

btc-payment: the protocol fee in sats

toAddress
string

btc-sighash: where the spend pays

psbtBase64
string

btc-sighash

sighashHex
string

btc-sighash: equals sighashHexes[0]

sighashHexes
string[]

btc-sighash: one per input, same key

feeSats
integer

btc-sighash: the network fee

preimageHex
string

btc-sighash, claim: the secret you sent, to pass back on broadcast

timelockUnix
integer

refund (btc-sighash, solana-tx): the leg timelock

escrow
string

solana-tx: the escrow account

transactionBase64
string

solana-tx: the unsigned transaction

blockhash
string

solana-tx

lastValidBlockHeight
integer

solana-tx: rebuild once the chain passes it

transactions
object[]

tron-txid: unsigned transactions (a TRC-20 fund is approve, then fund)