Earn with Spark

Your user sends USDC to an executable address, which deposits it into Spark Savings USDC on Base, and the savings shares, sUSDC, go to your user’s wallet. They never connect their wallet to your app, and never approve anything.

1. Get an API key

   Create one in the dashboard, and keep it on your server. From a web page, use a client ID instead.

2. The contracts

   Everything happens on Base. The intent calls these contracts, and nothing else:

   Contract	Address	Why
   USDC	0x8335…2913	The token your user deposits.
   Spark Savings USDC	0x3128…e858	Spark’s savings vault for USDC (sUSDC): an ERC-4626 vault that earns the Sky Savings Rate.

3. The intent

   The token is USDC, and the amount is in its base units: USDC has 6 decimals, so 100 USDC is "100000000". Once the address holds exactly the amount, it makes these calls, as itself, in one transaction:

   1approve(address spender, uint256 amount)on USDC

   An ERC-4626 deposit pulls its assets with transferFrom, so the address first allows the vault to take exactly the amount, and no more.

   Argument	Value	Why
   spender	0x3128…e858	The vault, which takes the USDC in the next call.
   amount	$AMOUNT	Exactly the deposit, so nothing is left approved afterwards.

   2deposit(uint256 assets, address receiver)on Spark Savings USDC

   The ERC-4626 deposit: the vault takes the USDC and mints sUSDC to receiver.

   Argument	Value	Why
   assets	$AMOUNT	All of the USDC.
   receiver	$WALLET	Your user’s wallet: the sUSDC is theirs.

   recovery is $WALLET: your user’s wallet, so if the deposit can’t happen, their USDC goes straight back to them.

4. Create the address

   Post the intent to Create an address. The expiry is 5 minutes away and the salt is random, so every run gives a new address:

   AMOUNT=100000000   # the deposit in base units: 100 USDC
   WALLET=0x…         # your user’s wallet
   
   curl https://api.execute.cash/v1/address/create \
     -H "Authorization: Bearer $EXECUTE_API_KEY" \
     -H "Content-Type: application/json" \
     -d '{
       "token": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
       "amount": "'$AMOUNT'",
       "calls": [
         {
           "target": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
           "function": "approve(address spender, uint256 amount)",
           "args": ["0x3128a0F7f0ea68E7B7c9B00AFa7E41045828e858", "'$AMOUNT'"]
         },
         {
           "target": "0x3128a0F7f0ea68E7B7c9B00AFa7E41045828e858",
           "function": "deposit(uint256 assets, address receiver)",
           "args": ["'$AMOUNT'", "'$WALLET'"]
         }
       ],
       "expirationTimestamp": '$(( $(date +%s) + 300 ))',
       "recovery": "'$WALLET'",
       "salt": "0x'$(openssl rand -hex 32)'",
       "chainId": 8453
     }'

   The response’s address is the executable address. Check it as the quickstart shows before you show it to anyone.

5. Show it to your user

   Show the address with the exact amount, the token and the chain, in words, and a way to copy each. Beside them, a QR code of an EIP-681 payment request lets your user’s wallet fill in the chain, the token and the amount by itself:

   // address and intent, from the create response
   const request = `ethereum:${intent.token}@${intent.chainId}/transfer?address=${address}&uint256=${intent.amount}`;

   uint256 is in the token’s base units, like the intent’s amount. Say under the code what it fills in, and offer a plain code of the address alone for wallets that can’t read a request; your user then picks the token and chain and enters the amount themselves. The address’s page, execute.cash/address/<address>, shows your user what paying it will do.

   Your user pays with an ordinary transfer, from any wallet or exchange. They connect nothing and approve nothing.

6. Track it

   Poll the address’s status, or get webhooks. Once it’s settled, your user’s wallet holds sUSDC. It grows in value at the Sky Savings Rate, and redeems for USDC at any time, from any app that supports Spark.