Transfer SPL Token (USDC)

Send any SPL token (e.g. USDC) from one Solana wallet to another. Automatically resolves Associated Token Accounts (ATAs) — creates the recipient ATA if needed.

Components used:

• GET_SOLANA_ACCOUNT_BALANCE — check SPL token balance
• BUILD_SOLANA_TRANSFER_INSTRUCTION — build SPL transfer instruction (resolves ATAs automatically)
• BUILD_SOLANA_TRANSACTION — construct the unsigned transaction
• SIGN_WITH_KEY_SHARE — MPC sign (Ed25519)
• BUILD_SOLANA_SIGNATURE_PAIR_ITEM — wrap the signature
• SIGN_SOLANA_TRANSACTION — finalize the signed transaction
• BROADCAST_SOLANA_TRANSACTION — submit to the network

---

Code

import { WorkspaceClient, ComponentModule } from 'caller-sdk';

const workspace = new WorkspaceClient({ apiKey: process.env.WR_API_KEY! });

const RPC_URL  = 'https://api.mainnet-beta.solana.com';
const KEY_ID   = 'your-key-id';
const DERIV    = [2147483692, 2147484149, 2147483648, 0]; // m/44'/501'/0'/0'
const FROM     = 'FROMpubkey...'; // base58 sender address
const TO       = 'TOPubkey...';   // base58 recipient address

// USDC on Solana mainnet
const USDC_MINT = 'EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v';

async function transferUsdc(rawAmount: string) {
  // 1. Check USDC balance (returned as hex string)
  const { value } = await workspace
    .call(ComponentModule.GET_SOLANA_ACCOUNT_BALANCE, {
      jsonRpcUrl: RPC_URL,
      account: FROM,
      tokenMint: USDC_MINT,
    })
    .promise();

  console.log(`USDC balance: ${BigInt(value)} raw units`);
  if (BigInt(value) < BigInt(rawAmount)) throw new Error('Insufficient USDC balance');

  // 2. Build SPL transfer instruction
  //    Automatically resolves ATAs; creates recipient ATA if missing
  const { instructions } = await workspace
    .call(ComponentModule.BUILD_SOLANA_TRANSFER_INSTRUCTION, {
      jsonRpcUrl: RPC_URL,
      from: FROM,
      to: TO,
      amount: rawAmount,
      tokenMint: USDC_MINT,
    })
    .promise();

  // 3. Build unsigned transaction (no direct lamport transfer — only instructions)
  const { unsignedTransaction, serializedHash } = await workspace
    .call(ComponentModule.BUILD_SOLANA_TRANSACTION, {
      jsonRpcUrl: RPC_URL,
      feePayer: FROM,
      from: null,
      to: null,
      lamports: '0',
      instructions,
      nonceAccount: null,
    })
    .promise();

  // 4. MPC sign
  const { signature } = await workspace
    .call(ComponentModule.SIGN_WITH_KEY_SHARE, {
      keyId: KEY_ID,
      derivationPath: DERIV,
      messageHash: serializedHash,
    })
    .promise();

  // 5. Wrap + sign + broadcast
  const { item } = await workspace
    .call(ComponentModule.BUILD_SOLANA_SIGNATURE_PAIR_ITEM, {
      publicKey: FROM,
      signature,
    })
    .promise();

  const { signedTransaction } = await workspace
    .call(ComponentModule.SIGN_SOLANA_TRANSACTION, {
      unsignedTransaction,
      signatures: [item],
    })
    .promise();

  const { transactionSignature } = await workspace
    .call(ComponentModule.BROADCAST_SOLANA_TRANSACTION, {
      jsonRpcUrl: RPC_URL,
      signedTransaction,
    })
    .promise();

  console.log('Transaction:', transactionSignature);
  return transactionSignature;
}

// Send 5 USDC (USDC has 6 decimals: 5 * 1_000_000 = 5_000_000)
const sig = await transferUsdc('5000000');

---

Workflow canvas layout

GET_SOLANA_ACCOUNT_BALANCE (tokenMint = USDC)
         │ value (guard check)
         ▼
BUILD_SOLANA_TRANSFER_INSTRUCTION (tokenMint = USDC)
         │ instructions[]
         ▼
BUILD_SOLANA_TRANSACTION
         │ serializedHash          │ unsignedTransaction
         ▼                         │
SIGN_WITH_KEY_SHARE                │
         │ signature               │
         ▼                         │
BUILD_SOLANA_SIGNATURE_PAIR_ITEM   │
         │ item                    │
         └──────────┬──────────────┘
                    ▼
         SIGN_SOLANA_TRANSACTION
                    │ signedTransaction
                    ▼
         BROADCAST_SOLANA_TRANSACTION
                    │ transactionSignature
                    ▼
              [Confirmed]

ATA creation

If the recipient does not yet have a USDC ATA, BUILD_SOLANA_TRANSFER_INSTRUCTION automatically includes an createAssociatedTokenAccount instruction. The sender pays the ATA rent (~0.002 SOL).