Ethereum & EVM

API Endpoints

1. Estimate Transaction Fee

POST /transactions/estimate - Get estimated gas fees before sending

2. Create EVM Transaction

POST /transactions - Create and send Ethereum/EVM transactions

Estimate Transaction Fees

Before creating EVM transactions, estimate gas fees to optimize transaction costs and ensure sufficient funds.

Endpoint

POST /transactions/estimate

Request Headers

Content-Type: application/json
Authorization: Bearer <encodedToken>

Parameters

Parameter	Type	Required	Description
`chain`	string	Yes	EVM chain (ETHEREUM, POLYGON, BSC, etc.)
`walletId`	string	Yes	Unique identifier for the wallet
`token`	string	Yes	Token type (ETH, USDC, USDT, etc.)
`tos`	array	Yes	Array of destination objects
`from`	array	No	Array of sender addresses
`operation`	string	No	Operation type (transfer, approve, transferFrom)

Example Request

curl --request POST \
     --url https://developers.bitpowr.com/api/v1/transactions/estimate \
     -H 'content-type: application/json' \
     -H 'authorization: Bearer <encodedToken>' \
     -d '{
          "chain": "ETHEREUM",
          "walletId": "e3455-15b5-46ad-84de-34555",
          "token": "USDC",
          "tos": [{
              "address": "0x1180a4c0c71b5eb0256edcffcc3389f1f085c502",
              "value": "100"
          }],
          "from": ["0x40fa00fe4a0a655240fede3149e9ea55118241e2"]
      }'

Response Format

{
  "fee": {
    "fast": {
      "gasFee": "0.000119673736860231",
      "gasLimit": 46467,
      "gasPrice": "2575456493"
    },
    "slow": {
      "gasFee": "0.0000697005",
      "gasLimit": 46467,
      "gasPrice": "1500000000"
    },
    "medium": {
      "gasFee": "0.000049973236860231",
      "gasLimit": 46467,
      "gasPrice": "1075456493"
    }
  }
}

EVM Transaction Parameters

Core Parameters

Parameter	Type	Required	Description
`walletId`	string	Yes	Unique identifier for the wallet
`assetType`	string	Yes	Asset type (ETH, USDC, USDC_BASE, etc.)
`tos`	array	Yes	Array of destination objects
`from`	array	No	Array of sender addresses
`description`	string	No	Transaction description

Gas Management Parameters

Parameter	Type	Description
`gasLimit`	string	Maximum gas units to use for the transaction
`gasPrice`	string	Gas price in wei (for legacy transactions)
`fee`	string	Transaction fee in ETH (alternative to gasPrice)

Advanced Parameters

Parameter	Type	Description
`operation`	string	Operation type (transfer, approve, transferFrom)
`spenderAddress`	string	Address to approve for spending (approve operations)
`feeAddress`	string	Address to pay transaction fees (transferFrom operations)

Output Object Structure

Parameter	Type	Required	Description
`address`	string	Yes	Recipient Ethereum address (0x...)
`value`	string	Yes	Amount to send (in token units)

EVM Transaction Types

1. Send Ethereum (ETH) Transaction

Send native ETH on Ethereum or native tokens on other EVM chains.

Basic ETH Transfer

curl --request POST \
     --url https://developers.bitpowr.com/api/v1/transactions \
     -H 'content-type: application/json' \
     -H 'authorization: Bearer <encodedToken>' \
     -d '{
          "walletId": "e3455-15b5-46ad-84de-34555",
          "assetType": "ETH",
          "from": ["0x40fa00fe4a0a655240fede3149e9ea55118241e2"],
          "tos": [{
              "address": "0x1180a4c0c71b5eb0256edcffcc3389f1f085c502",
              "value": "0.01"
          }],
          "description": "ETH transfer"
      }'

ETH Transfer with Custom Gas

curl --request POST \
     --url https://developers.bitpowr.com/api/v1/transactions \
     -H 'content-type: application/json' \
     -H 'authorization: Bearer <encodedToken>' \
     -d '{
          "walletId": "e3455-15b5-46ad-84de-34555",
          "assetType": "ETH",
          "from": ["0x40fa00fe4a0a655240fede3149e9ea55118241e2"],
          "tos": [{
              "address": "0x1180a4c0c71b5eb0256edcffcc3389f1f085c502",
              "value": "0.01"
          }],
          "fee": 0.0001,
          "gasLimit": "21000",
          "gasPrice": "2000000000",
          "description": "ETH transfer with custom gas"
      }'

2. Send ERC20 Token Transaction

Send ERC20 tokens like USDC, USDT, or other standard tokens on Ethereum and EVM-compatible chains.

USDC on Ethereum

curl --request POST \
     --url https://developers.bitpowr.com/api/v1/transactions \
     -H 'content-type: application/json' \
     -H 'authorization: Bearer <encodedToken>' \
     -d '{
          "walletId": "e3455-15b5-46ad-84de-34555",
          "assetType": "USDC",
          "from": ["0x40fa00fe4a0a655240fede3149e9ea55118241e2"],
          "tos": [{
              "address": "0x1180a4c0c71b5eb0256edcffcc3389f1f085c502",
              "value": "100"
          }],
          "description": "USDC transfer on Ethereum"
      }'

USDC on Base

curl --request POST \
     --url https://developers.bitpowr.com/api/v1/transactions \
     -H 'content-type: application/json' \
     -H 'authorization: Bearer <encodedToken>' \
     -d '{
          "walletId": "e3455-15b5-46ad-84de-34555",
          "assetType": "USDC_BASE",
          "from": ["0x40fa00fe4a0a655240fede3149e9ea55118241e2"],
          "tos": [{
              "address": "0x1180a4c0c71b5eb0256edcffcc3389f1f085c502",
              "value": "100"
          }],
          "description": "USDC transfer on Base"
      }'

ERC20 Transfer with Custom Gas

curl --request POST \
     --url https://developers.bitpowr.com/api/v1/transactions \
     -H 'content-type: application/json' \
     -H 'authorization: Bearer <encodedToken>' \
     -d '{
          "walletId": "e3455-15b5-46ad-84de-34555",
          "assetType": "USDC",
          "from": ["0x40fa00fe4a0a655240fede3149e9ea55118241e2"],
          "tos": [{
              "address": "0x1180a4c0c71b5eb0256edcffcc3389f1f085c502",
              "value": "100"
          }],
          "fee": 0.01,
          "gasLimit": "65000",
          "gasPrice": "2000000000",
          "description": "USDC transfer with custom gas"
      }'

3. Send Transaction with Custom Gas Parameters

Control transaction fees precisely by specifying gas limit, gas price, and fee parameters.

All Gas Parameters Required

curl --request POST \
     --url https://developers.bitpowr.com/api/v1/transactions \
     -H 'content-type: application/json' \
     -H 'authorization: Bearer <encodedToken>' \
     -d '{
          "walletId": "e3455-15b5-46ad-84de-34555",
          "assetType": "USDC",
          "from": ["0x40fa00fe4a0a655240fede3149e9ea55118241e2"],
          "tos": [{
              "address": "0x1180a4c0c71b5eb0256edcffcc3389f1f085c502",
              "value": "50"
          }],
          "gasLimit": "65000",
          "gasPrice": "3000000000",
          "fee": "0.000195",
          "description": "Transaction with all custom gas parameters"
      }'

Gas Parameter Guidelines:

gasLimit: 21000 for ETH transfers, 65000+ for ERC20 transfers
gasPrice: In wei (1 gwei = 1,000,000,000 wei)
fee: Total transaction fee in ETH (gasLimit × gasPrice ÷ 10^18)

Fee Calculation:

fee = (gasLimit × gasPrice) ÷ 1,000,000,000,000,000,000
Example: (65000 × 3000000000) ÷ 10^18 = 0.000195 ETH

4. Approve and TransferFrom Workflow

The approve/transferFrom pattern allows one address to spend tokens on behalf of another. This is commonly used for DeFi applications, payment processors, and automated trading systems.

Step 1: Send Approve Transaction

First, approve a spender address to spend a specific amount of tokens on your behalf.

curl --request POST \
     --url https://developers.bitpowr.com/api/v1/transactions \
     -H 'content-type: application/json' \
     -H 'authorization: Bearer <encodedToken>' \
     -d '{
          "walletId": "0722efe5-1d0a-41ae-9d7f-b22374062f81",
          "assetType": "USDC",
          "from": ["0x40fa00fe4a0a655240fede3149e9ea55118241e2"],
          "tos": [{
              "address": "0xA0b86a33E6A8b5E1e8eb7e0D8E5C9b8a52C9c3A8",
              "value": "1000"
          }],
          "spenderAddress": "0x1180a4c0c71b5eb0256edcffcc3389f1f085c502",
          "operation": "approve",
          "gasLimit": "50000",
          "gasPrice": "2000000000",
          "fee": "0.0001",
          "description": "Approve 1000 USDC for spender"
      }'

Approve Transaction Parameters:

tos[0].address: The spenderAddress in this case
tos[0].value: Total allowance amount (not per-transaction limit)
spenderAddress: Address that will be allowed to spend your tokens
operation: Must be "approve"

Step 2: Wait for Confirmation

Monitor the approve transaction until it's confirmed on the blockchain. You can check the transaction status using the returned transaction hash.

Step 3: Send TransferFrom Transaction

After the approve transaction is confirmed, the spender address can execute transferFrom operations.

curl --request POST \
     --url https://developers.bitpowr.com/api/v1/transactions \
     -H 'content-type: application/json' \
     -H 'authorization: Bearer <encodedToken>' \
     -d '{
          "walletId": "0722efe5-1d0a-41ae-9d7f-b22374062f81",
          "assetType": "USDC",
          "from": ["0x40fa00fe4a0a655240fede3149e9ea55118241e2"],
          "tos": [{
              "address": "0x742d35Cc6644C0532925a3b8C17DAb6F2c8f1234",
              "value": "250"
          }],
          "feeAddress": "0x1180a4c0c71b5eb0256edcffcc3389f1f085c502",
          "operation": "transferFrom",
          "gasLimit": "70000",
          "gasPrice": "2000000000",
          "fee": "0.00014",
          "description": "Transfer 250 USDC from approved allowance"
      }'

TransferFrom Transaction Parameters:

from[0]: Original token owner's address (must have approved the feeAddress)
tos[0].address: Final recipient of the tokens
tos[0].value: Amount to transfer (must not exceed approved allowance)
feeAddress: Address that pays gas fees (must be the approved spender)
operation: Must be "transferFrom"

Approve/TransferFrom Process Flow

1. Token Owner (0x40fa...) approves Spender (0x1180...)
   ↓
2. Approve transaction confirms on blockchain
   ↓
3. Spender (0x1180...) can now execute transferFrom
   ↓
4. TransferFrom moves tokens from Owner to Recipient
   ↓
5. Spender pays gas fees, Owner's tokens are transferred

Use Cases for Approve/TransferFrom

Payment Processors: Allow a service to spend tokens on behalf of users
DeFi Protocols: Enable smart contracts to move user tokens
Automated Trading: Let trading bots execute transactions with user funds
Subscription Services: Allow recurring payments from user wallets
Corporate Wallets: Enable employees to spend from company accounts

Important Notes

Allowance Management: The approved amount is the total allowance, not per-transaction
Security: Only approve trusted addresses with the minimum necessary allowance
Gas Costs: Both approve and transferFrom operations require gas fees
Allowance Tracking: Monitor remaining allowance after each transferFrom
Revoke Approval: Set allowance to "0" to revoke spending permissions

Transaction Response Format

All EVM transaction requests return a standardized response.

{
  "status": "success",
  "data": {
    "hash": "0x8f2a5b3c9d1e4f6a7b8c9d0e1f2a3b4c5d6e7f8a9b0c1d2e3f4a5b6c7d8e9f0a",
    "status": "PENDING",
    "amount": "100",
    "uid": "6680c116-c803-4e46-aa99-2f261cd216ac",
    "assetType": "USDC",
    "chain": "ETHEREUM",
    "fee": "0.000195",
    "gasLimit": "65000",
    "gasPrice": "3000000000",
    "ref": "BTP-EthTx123#ABC456",
    "network": "MAINNET"
  }
}

Response Fields

Field	Type	Description
`hash`	string	Ethereum transaction hash (0x...)
`status`	string	Transaction status (PENDING, CONFIRMED, FAILED)
`amount`	string	Amount sent in token units
`uid`	string	Unique BitPowr transaction identifier
`assetType`	string	Token type (ETH, USDC_ETH, etc.)
`chain`	string	Blockchain name (ETHEREUM, POLYGON, BSC)
`fee`	string	Transaction fee paid in ETH
`gasLimit`	string	Gas limit used
`gasPrice`	string	Gas price in wei
`ref`	string	BitPowr reference number
`network`	string	Network type (MAINNET or TESTNET)

EVM Workflow Examples

1. Basic Token Transfer Workflow

1. Estimate fees → POST /estimate-transaction
2. Create transaction → POST /transactions
3. Monitor confirmation using transaction hash

2. Custom Gas Management Workflow

1. Check current network gas prices
2. Calculate optimal gasLimit and gasPrice
3. Create transaction with custom gas parameters
4. Monitor transaction speed and adjust for future transactions

3. Approve/TransferFrom Workflow

1. Send approve transaction with total allowance
2. Wait for approve transaction confirmation
3. Send transferFrom transaction(s) as needed
4. Monitor remaining allowance
5. Revoke or adjust allowance when done

Best Practices

Gas Management

Estimate First: Always estimate gas fees before transactions
Buffer Gas Limit: Add 10-20% buffer to estimated gas limit
Monitor Network: Check network congestion for optimal gas prices
Priority Fees: Use higher gas prices for urgent transactions

Security

Address Validation: Verify all addresses before sending transactions
Amount Verification: Double-check token amounts and decimals
Allowance Limits: Only approve the minimum necessary allowance
Regular Monitoring: Track transaction status and confirmations

Error Handling

Insufficient Funds: Check ETH balance for gas fees
Gas Estimation Failures: Increase gas limit or check contract interactions
Nonce Issues: Handle nonce management for multiple transactions
Network Congestion: Implement retry logic with adjusted gas prices

Address Format & Requirements

Ethereum Addresses

Format: Hexadecimal strings starting with 0x
Length: 42 characters (including 0x prefix)
Case: Case-insensitive, but checksummed addresses preferred
Example: 0x742d35Cc6644C0532925a3b8C17DAb6F2c8f1234

Gas Units Guidelines

ETH Transfer: 21,000 gas
ERC20 Transfer: 65,000 - 100,000 gas
ERC20 Approve: 45,000 - 60,000 gas
TransferFrom: 70,000 - 100,000 gas

Common Gas Prices (in Gwei)

Slow: 10-20 Gwei (10,000,000,000 - 20,000,000,000 wei)
Standard: 20-30 Gwei (20,000,000,000 - 30,000,000,000 wei)
Fast: 30-50 Gwei (30,000,000,000 - 50,000,000,000 wei)
Urgent: 50+ Gwei (50,000,000,000+ wei)