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POST
/
v1
/
transactions
/
build
Build Transaction
curl --request POST \
  --url https://api.example.com/v1/transactions/build \
  --header 'Content-Type: application/json' \
  --data '
{
  "fromAddress": "<string>",
  "toAddress": "<string>",
  "amount": "<string>",
  "chainReference": "<string>",
  "chainId": "<string>",
  "contractAddress": "<string>",
  "gasLimit": "<string>",
  "gasPrice": "<string>",
  "nonce": "<string>",
  "memo": "<string>"
}
'
{
  "txId": "<string>",
  "unsignedTxHex": "<string>",
  "signHashes": [
    {}
  ],
  "metadata": {
    "nonce": "<string>",
    "gasLimit": "<string>",
    "gasPrice": "<string>",
    "maxFeePerGas": "<string>",
    "maxPriorityFeePerGas": "<string>",
    "chainId": "<string>"
  }
}

​
Build Transaction

Construct an unsigned transaction for native token or ERC-20 transfers. The response includes the unsigned transaction hex and hash(es) to sign.

​
Request

​
fromAddress
string
required
Sender address
​
toAddress
string
required
Recipient address
​
amount
string
required
Amount in smallest unit (wei for ETH, lamports for SOL)
​
chainReference
string
required
Chain identifier (e.g., eip155:1 for Ethereum mainnet)
​
chainId
string
Numeric chain ID (e.g., 1 for Ethereum)
​
contractAddress
string
Token contract address (for ERC-20 transfers)
​
gasLimit
string
Gas limit (optional, auto-estimated if not provided)
​
gasPrice
string
Gas price in wei (optional, auto-estimated if not provided)
​
nonce
string
Transaction nonce (optional, auto-fetched if not provided)
​
memo
string
Optional memo/data field

​
Response

​
txId
string
Internal transaction identifier
​
unsignedTxHex
string
Unsigned transaction in hex format
​
signHashes
array
Array of hashes to sign
​
metadata
object
Transaction metadata

​
Example

curl -X POST https://api.axonvault.io/v1/transactions/build \
  -H "X-Access-Key: ak_live_abc123" \
  -H "X-Signature: 5d41402abc4b2a76b9719d911017c592" \
  -H "X-Timestamp: 2024-01-15T10:30:00Z" \
  -H "Content-Type: application/json" \
  -d '{
    "fromAddress": "0x742d35Cc6634C0532925a3b844Bc9e7595f8fE8d",
    "toAddress": "0x1234567890123456789012345678901234567890",
    "amount": "1000000000000000000",
    "chainReference": "eip155:1",
    "chainId": "1"
  }'

​
Response Example

{
  "txId": "tx_abc123",
  "unsignedTxHex": "0xf86c0a8502540be400825208941234567890123456789012345678901234567890880de0b6b3a76400008025a0...",
  "signHashes": [
    "0xabc123def456789..."
  ],
  "metadata": {
    "nonce": "10",
    "gasLimit": "21000",
    "gasPrice": "20000000000",
    "chainId": "1",
    "chainReference": "eip155:1"
  }
}

​
Errors

Error TypeStatusDescription
invalid_request400Missing required fields
invalid_address400Invalid from or to address
insufficient_balance400Not enough funds
policy_denied403Transaction blocked by policy

​
ERC-20 Transfer Example

curl -X POST https://api.axonvault.io/v1/transactions/build \
  -H "X-Access-Key: ak_live_abc123" \
  -H "X-Signature: ..." \
  -H "X-Timestamp: 2024-01-15T10:30:00Z" \
  -H "Content-Type: application/json" \
  -d '{
    "fromAddress": "0x742d35Cc6634C0532925a3b844Bc9e7595f8fE8d",
    "toAddress": "0x1234567890123456789012345678901234567890",
    "amount": "1000000",
    "chainReference": "eip155:1",
    "contractAddress": "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48"
  }'

​
Next Steps

After building a transaction:
  1. Sign the transaction
  2. Construct signed transaction
  3. Submit to blockchain