{
     "jsonrpc": "2.0",
     "id": 1,
     "method": "eth_sendBundle",
     "params": [
          {
               txs, // Array[String], A list of signed transactions to execute in an atomic bundle, list can be empty for bundle cancellations
               blockNumber, // (Optional) String, a hex-encoded block number for which this bundle is valid. Default, current block number
               minTimestamp, // (Optional) Number, the minimum timestamp for which this bundle is valid, in seconds since the unix epoch
               maxTimestamp, // (Optional) Number, the maximum timestamp for which this bundle is valid, in seconds since the unix epoch
               revertingTxHashes, // (Optional) Array[String], A list of tx hashes that are allowed to revert or be discarded
               replacementUuid, // (Optional) String, any arbitrary string that can be used to replace or cancel this bundle
          }
     ]
}

Important: If the refundPercent field is set, the builder will construct a refund transaction automatically. However, if the refund amount does not cover the cost of the transaction (i.e., gas_used * base_fee), the bundle will be discarded. ‍

Refund Example

Consider the following Bundle:

• • TXN 1 – User swap (Base fee: 50 Gwei, Piority fee 3 Gwei, Gas: 280k)
  • TXN 2 – Backrun (Base fee: 50 Gwei, Priority fee 100 Gwei, Gas: 150k)
  • refundPercent: 90%
  • Current block base fee: 50 Gwei

Calculation:

• ETH reward of the last transaction in the bundle = (150k x 100 Gwei) = 15,000 Gwei
• ETH reward after transfer transaction fees = 15000 – (21k x 50 Gwei) = 13,950 Gwei
• Refund amount = 0.9 x 13,950 Gwei = 12,555 Gwei‍

CURL example

curl -s --data '{"jsonrpc": "2.0","id": "1","method": "eth_sendBundle","params": [{"txs": ["0x12…ab","0x34..cd"], "blockNumber": "0x102286B","replacementUuid": "abcd1234"}]}' -H "Content-Type: application/json" -X POST https://rpc.btcs.com

Response example

{"result":{"bundleHash":"0x164d7d41f24b7f333af3b4a70b690cf93f636227165ea2b699fbb7eed09c46c7"},"error":null,"id":1}

Bundle Hash

Here is the algorithm for determining the bundle hash:

// Bundle hash implementation.
// Different to standard as we include Block Number and Replacement UUID.
func (b *BundleArgs) Hash() common.Hash {
     bundleHasher := sha3.NewLegacyKeccak256()

     bundleHasher.Write([]byte(b.BlockNumber))
     bundleHasher.Write([]byte(b.ReplacementUuid))
     for _, tx := range b.Txs {
          bundleHasher.Write(tx.Hash)
     }
     bundleHash := common.BytesToHash(bundleHasher.Sum(nil))

     return bundleHash
}