Quickstart: Deposit into an Earn vault

Earn yield on your USDC by depositing it into a Morpho vault on Arc Testnet. This quickstart uses Circle Wallets, but you can use any compatible adapter setup.

Prerequisites

Before you begin, ensure that you’ve:

Installed Node.js v22+.
Obtained an API key and entity secret from the Circle Console.
Created a developer-controlled wallet on Arc Testnet using the Circle Console.
Funded your Arc Testnet wallet with testnet USDC from the Circle Faucet.

Earn operations work without an API key. For higher rate limits, pass an optional API key as apiKey in the operation config. Keep the API key server-side. The App Kit SDK rejects an API key passed from a browser context.

Example: passing an API key

TypeScript

const result = await kit.earn.deposit({
  from: { adapter, chain: "Arc_Testnet" },
  vaultAddress: "0x...",
  amount: "10.00",
  config: { apiKey: process.env.API_KEY as string },
});

Step 1. Set up the project

1.1. Create the project and install dependencies

Create a new directory and install the App Kit SDK with the Circle Wallets adapter and supporting tools:

Shell

# Set up your directory and initialize a Node.js project
mkdir app-kit-earn-deposit-circle-wallets
cd app-kit-earn-deposit-circle-wallets
npm init -y
npm pkg set type=module

# Set up run scripts
npm pkg set scripts.explore-vaults="tsx --env-file=.env explore-vaults.ts"
npm pkg set scripts.deposit="tsx --env-file=.env deposit.ts"

# Install runtime dependencies
npm install @circle-fin/app-kit @circle-fin/adapter-circle-wallets tsx

# Install dev dependencies
npm install --save-dev typescript @types/node

Only need Earn and want a lighter install than the full App Kit? Install the standalone package instead: @circle-fin/earn-kit

1.2. Configure TypeScript (optional)

This step is optional. It helps prevent missing types in your IDE or editor.

Create a tsconfig.json file configured for ESM and Node:

Shell

cat <<'EOF' > tsconfig.json
{
  "compilerOptions": {
    "target": "ESNext",
    "module": "ESNext",
    "moduleResolution": "bundler",
    "strict": true,
    "types": ["node"]
  }
}
EOF

1.3. Set environment variables

Create an .env file in the project directory:

Shell

touch .env

Add your credentials. Replace YOUR_API_KEY with your Circle Developer API key, YOUR_ENTITY_SECRET with your entity secret:

.env

CIRCLE_API_KEY=YOUR_API_KEY
CIRCLE_ENTITY_SECRET=YOUR_ENTITY_SECRET

Edit .env files in your IDE or editor so credentials are not leaked to your shell history.

Step 2. Discover available vaults

kit.earn.exploreVaults returns the vaults available on a chain along with each vault’s address, current APY, fees, and status. Use it to pick a vault to deposit into.

2.1. Create the discovery script

Create an explore-vaults.ts file:

explore-vaults.ts

import { AppKit } from "@circle-fin/app-kit";

const kit = new AppKit();

async function main() {
  const { vaults, pagination } = await kit.earn.exploreVaults({
    chain: "Arc_Testnet",
    sortBy: "apy",
  });

  console.log(`Found ${pagination.totalCount} vaults`);
  console.dir(vaults, { depth: null, colors: true });
}

void main();

kit.earn.exploreVaults accepts filter, sort, and pagination parameters such as protocol, asset, minApy, minTvl, sortBy, page, and pageSize. For lazy iteration across all pages, use kit.earn.exploreVaultsIterator.

2.2. Run the discovery script

In your terminal, run:

Shell

npm run explore-vaults

You’ll see output like:

Shell

Found 4 vaults
[
  {
    vaultAddress: '0x...',
    chain: 'Arc_Testnet',
    name: 'Steakhouse USDC',
    protocol: 'MORPHO',
    asset: 'USDC',
    assetAddress: "0x...",
    currentApy: 0.042,
    nativeApy: 0,
    vaultFee: 0,
    rewards: [],
    collateral: [],
    status: "active",
    circleGuarded: false,
    totalDeposits: "0.0",
    liquidity: "1000000.0",
  },
  ...
]

Only deposit into a vault with status: 'active'. A 'low_liquidity' vault may not have enough liquidity for withdrawals.

kit.earn.exploreVaults returns all Morpho vaults on the blockchain. No allowlist is applied, so integrators choose any active vault to deposit into. Crosschain deposits are an exception: gas-sponsored crosschain routes use a manually allowlisted set of destination vaults.

2.3. Pick a vault

Choose a vault from the output and copy its vaultAddress. You’ll use it in the next step.

Step 3. Deposit USDC

If your wallet is on a different blockchain than the vault, see Deposit crosschain into an Earn vault instead.

3.1. Create the deposit script

Create a deposit.ts file. Replace YOUR_SELECTED_VAULT_ADDRESS with the vault address you copied in the previous step and YOUR_CIRCLE_WALLET_ADDRESS with the address of your Circle Wallets wallet. This script deposits 10.00 USDC into the vault:

Pass amount as a positive decimal string (for example "10.00"). Zero and negative values are rejected. For USDC and EURC, use at most 6 decimal places. Leading zeros and leading-dot forms (for example "00.5" or ".5") are rejected.

deposit.ts

import { AppKit } from "@circle-fin/app-kit";
import { createCircleWalletsAdapter } from "@circle-fin/adapter-circle-wallets";

const kit = new AppKit();
const amount = "10.00";
const vaultAddress = "YOUR_SELECTED_VAULT_ADDRESS";

const adapter = createCircleWalletsAdapter({
  apiKey: process.env.CIRCLE_API_KEY!,
  entitySecret: process.env.CIRCLE_ENTITY_SECRET!,
});

async function main() {
  const result = await kit.earn.deposit({
    from: {
      adapter,
      chain: "Arc_Testnet",
      address: "YOUR_CIRCLE_WALLET_ADDRESS",
    },
    vaultAddress,
    amount,
  });

  console.dir(result, { depth: null, colors: true });
}

void main();

Preview the expected outcome of a deposit before submitting with kit.earn.getDepositQuote.

3.2. Run the deposit script

In your terminal, run:

Shell

npm run deposit

When the script completes, you’ll see output like:

Shell

{
  kind: "same-chain",
  txHash: "0x...",
  explorerUrl: "https://explorer.testnet.arc.io/tx/0x...",
  vaultAddress: "0x...",
  amount: "10",
}

Use the txHash to verify the transaction on the Arc Testnet block explorer. To confirm the vault shares credited to your wallet, see Check your Earn position. When you’re ready to redeem, see Withdraw from an Earn vault.

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Quickstart: Deposit into an Earn vault

Prerequisites

Step 1. Set up the project

1.1. Create the project and install dependencies

1.2. Configure TypeScript (optional)

1.3. Set environment variables

Step 2. Discover available vaults

2.1. Create the discovery script

2.2. Run the discovery script

2.3. Pick a vault

Step 3. Deposit USDC

3.1. Create the deposit script

3.2. Run the deposit script

​Prerequisites

​Step 1. Set up the project

​1.1. Create the project and install dependencies

​1.2. Configure TypeScript (optional)

​1.3. Set environment variables

​Step 2. Discover available vaults

​2.1. Create the discovery script

​2.2. Run the discovery script

​2.3. Pick a vault

​Step 3. Deposit USDC

​3.1. Create the deposit script

​3.2. Run the deposit script

Prerequisites

Step 1. Set up the project

1.1. Create the project and install dependencies

1.2. Configure TypeScript (optional)

1.3. Set environment variables

Step 2. Discover available vaults

2.1. Create the discovery script

2.2. Run the discovery script

2.3. Pick a vault

Step 3. Deposit USDC

3.1. Create the deposit script

3.2. Run the deposit script