POST /wallet/send Initiate an on-chain transfer using a wallet you manage.

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Request (single-output)

{
  "api_key": "sk_live_...",
  "wallet_id": "w_c8b07c7d-9c7d-4a33-9200-0bdfa82dc497",
  "amount": 0.25,
  "destination": "0x742d35Cc6634C0532925a3b844Bc454e4438f44e",
  "asset": "ETH",
  "eth_fee": 65000,
  "eth_max_priority_fee_per_gas": 1700000000,
  "eth_max_fee_per_gas": 3500000000,
  "metadata": {
    "invoice": "INV-42",
    "customer_id": "cust_123"
  }
}
Bitcoin fee tier example: 
{
  "api_key": "sk_live_...",
  "wallet_id": "w_b1a2f3c4-5678-90ab-cdef-1234567890ab",
  "amount": 0.0015,
  "destination": "bc1qw508d6qejxtdg4y5r3zarvary0c5xw7kv8fn0d",
  "asset": "BTC",
  "btc_fee": "high"
}

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Request (BTC multi-output)

For Bitcoin you can send to multiple recipients in one transaction. Provide a mapping of destination addresses to amounts and omit the top-level amount: 
{
  "api_key": "sk_live_...",
  "wallet_id": "w_b1a2f3c4-5678-90ab-cdef-1234567890ab",
  "destination": {
    "bc1qaddr1...": 0.004,
    "bc1qaddr2...": 0.006
  },
  "asset": "BTC",
  "btc_fee": "normal",
  "metadata": { "batch": true }
}
FieldTypeRequiredNotes
api_keystring✓Customer API key.
wallet_idstring✓Wallet ID (w_<uuid>) or on-chain address.
amountnumber✓*Natural units (ETH, BTC, TRX, or token units). Required for single-output sends; omit for BTC multi-output.
destinationstring or object✓Single-output: recipient address as a string. BTC multi-output: object mapping { "address": amount }.
assetstring✓Supported values:
• ETH wallets → ETH, USDC, USDT
• BTC wallets → BTC
• Tron wallets → TRX, USDT
btc_feestring✕Optional BTC fee tier. Accepted values: low, normal, high. Defaults to the provider recommendation. May also accept a sat/vByte or sat/kByte string.
eth_feestring✕Optional Ethereum gas limit. Defaults to 21,000 for native ETH transfers and 65,000 for ERC-20 transfers.
eth_max_priority_fee_per_gasstring✕Optional for Ethereum. Tip paid to validators, expressed in wei. Must not exceed eth_max_fee_per_gas.
eth_max_fee_per_gasstring✕Optional for Ethereum. Total fee cap per gas unit in wei. Defaults to the API-estimated value when omitted.
metadataobject✕Optional JSON object stored on the resulting transaction. Keys must be strings and data must be JSON serializable.

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Response

Successful broadcast: 
{
  "result": "ok",
  "tx_id": "0x9345a5f6f4d0f7..."
}
Failed broadcast (HTTP 200): 
{
  "result": "fail",
  "tx_id": "Not enough TRX balance for transfer"
}
Use the result flag to decide whether to retry or alert an operator. A value of "ok" always includes the blockchain transaction hash in tx_id; a value of "fail" contains the upstream provider’s error string. Even when the result is "ok", final settlement still depends on miners or validators confirming the transaction on-chain.

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Errors

StatusPayloadWhen it happens
400{ "error": "Missing required fields" }Missing body parameters.
403{ "error": "API key is not valid" }API key fails validation.
404{ "result": "not_found" }Wallet does not exist or isn’t owned by your account.
400{ "error": "Wallet is not a BTC wallet" }Attempting to send BTC assets from a non-BTC wallet.
500{ "error": "<message>" }Unexpected service error.

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Bitcoin UTXO handling

When broadcasting BTC, 1151 first tries to cover the transfer amount(s) and miner fee with a single UTXO from the wallet. If no individual output is large enough, the platform selects the smallest possible combination of UTXOs to fulfill the spend. Any change output — including the remainder from consolidated UTXOs — is automatically returned to the wallet’s receiving address as a single UTXO.

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Operational tips

  • ERC-20 and TRC-20 transfers require the wallet to maintain enough native token (ETH/TRX) for gas or energy.
  • When customizing Ethereum gas, ensure eth_max_fee_per_gas is greater than or equal to eth_max_priority_fee_per_gas; otherwise broadcasts will fail client-side.
  • If you omit Ethereum gas overrides, the API uses current network estimates. Supply all three Ethereum-specific parameters when you want a fully custom gas configuration.
  • Metadata travels with the transaction so you can look it up later via /transaction/get or the SDK helpers.

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SDK equivalents

  • JavaScript: client.sendFromWallet({ walletId, asset, amount?, destination?, destinations?, btcFee?, ethFee?, ethMaxPriorityFeePerGas?, ethMaxFeePerGas?, metadata? }) or wallet.send({ asset, amount?, destination?, destinations?, ... })
  • Python: client.send_from_wallet(wallet_id, amount, destination, asset, metadata=None, btc_fee=None, ...) or wallet.send(amount=..., destination=..., asset=..., ...). For BTC multi-output in Python, pass a mapping for destination and omit amount.