Starknet Wallet

Starknet Wallet Skill

Manage Starknet wallets for AI agents with native Account Abstraction support.

When to Use

• Creating, funding, and operating Starknet accounts for agent workflows.
• Checking balances, sending transfers, managing session keys, or invoking contracts from an agent wallet.

When NOT to Use

• DeFi-specific routing, staking, or lending flows better covered by starknet-defi.
• Cairo contract authoring, deployment-only operations, or security auditing.

Quick Start

1. Install the SDK dependencies and set Starknet RPC/account environment variables.
2. Use skills catalog to pivot to adjacent modules like DeFi, deployment, or auditing.

Prerequisites

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npm install starknet@^10.8.0 @avnu/avnu-sdk@^4.2.0

Environment variables:

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STARKNET_RPC_URL=https://starknet-mainnet.g.alchemy.com/v2/YOUR_KEY
STARKNET_ACCOUNT_ADDRESS=0x...
STARKNET_PRIVATE_KEY=0x...
AVNU_BASE_URL=https://starknet.api.avnu.fi (optional)
AVNU_PAYMASTER_URL=https://starknet.paymaster.avnu.fi (optional)
AVNU_PAYMASTER_API_KEY=your_key (optional, for free gas)

Available MCP Tools

The Starknet MCP Server provides these tools for wallet operations:

Balance Tools Detail

starknet_get_balance (Single Token)

Query balance for one token. Use for simple cases.

Input:

• token (required): Token symbol (ETH, STRK, USDC, USDT) or contract address
• address (optional): Wallet address (defaults to agent's address)

Response:

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{
  "address": "0x...",
  "token": "ETH",
  "tokenAddress": "0x049d36570d4e46f48e99674bd3fcc84644ddd6b96f7c741b1562b82f9e004dc7",
  "balance": "1.5",
  "raw": "1500000000000000000",
  "decimals": 18
}

starknet_get_balances (Multiple Tokens)

Query balances for multiple tokens in a single RPC call. More efficient for portfolio views.

Input:

• tokens (required): Array of token symbols or addresses (max 200)
• address (optional): Wallet address

Response:

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{
  "address": "0x...",
  "balances": [
    { "token": "ETH", "tokenAddress": "0x...", "balance": "1.5", "raw": "...", "decimals": 18 },
    { "token": "USDC", "tokenAddress": "0x...", "balance": "100", "raw": "...", "decimals": 6 }
  ],
  "tokensQueried": 2,
  "method": "balance_checker"
}

When to use:

• starknet_get_balance: Quick single-token check
• starknet_get_balances: Portfolio overview, multi-token operations

Core Operations

Check Balance (Single Token)

Use the starknet_get_balance MCP tool for simple single-token queries:

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// Via MCP tool (recommended)
const result = await mcpClient.callTool({
  name: "starknet_get_balance",
  arguments: {
    address: "0x...",  // Account address
    token: "ETH",      // Symbol (ETH, STRK, USDC, USDT) or contract address
  }
});
// Returns: { address, token, tokenAddress, balance, raw, decimals }

Direct starknet.js usage:

typescriptCopy code
import { RpcProvider, Contract } from "starknet";

const provider = new RpcProvider({ nodeUrl: process.env.STARKNET_RPC_URL });

// ETH balance (starknet.js v10 uses an options object for Contract)
const ethAddress = "0x049d36570d4e46f48e99674bd3fcc84644ddd6b96f7c741b1562b82f9e004dc7";
const ethContract = new Contract({
  abi: erc20Abi,
  address: ethAddress,
  providerOrAccount: provider,
});
// starknet.js parses a Cairo 1 u256 return value to bigint (no low/high struct)
const balance: bigint = await ethContract.balanceOf(accountAddress);
// Format: (balance / 10n ** 18n).toString() for whole units

Check Multiple Balances (Batch)

Use starknet_get_balances for efficient multi-token queries (single RPC call):

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// Via MCP tool (recommended for multiple tokens)
const result = await mcpClient.callTool({
  name: "starknet_get_balances",
  arguments: {
    address: "0x...",
    tokens: ["ETH", "STRK", "USDC", "USDT"],  // Up to 200 tokens
  }
});

// Returns:
// {
//   address: "0x...",
//   balances: [
//     { token: "ETH", tokenAddress: "0x...", balance: "1.5", raw: "1500000000000000000", decimals: 18 },
//     { token: "STRK", tokenAddress: "0x...", balance: "100", raw: "100000000000000000000", decimals: 18 },
//     ...
//   ],
//   tokensQueried: 4,
//   method: "balance_checker"  // Uses BalanceChecker contract for efficiency
// }

Direct starknet.js usage with BalanceChecker contract:

typescriptCopy code
import { RpcProvider, Contract } from "starknet";

const provider = new RpcProvider({ nodeUrl: process.env.STARKNET_RPC_URL });

// BalanceChecker contract (returns non-zero balances only)
const BALANCE_CHECKER_ADDRESS = "0x031ce64a666fbf9a2b1b2ca51c2af60d9a76d3b85e5fbfb9d5a8dbd3fedc9716";
const BALANCE_CHECKER_ABI = [
  {
    type: "struct",
    name: "core::integer::u256",
    members: [
      { name: "low", type: "core::integer::u128" },
      { name: "high", type: "core::integer::u128" },
    ],
  },
  {
    type: "struct",
    name: "governance::balance_checker::NonZeroBalance",
    members: [
      { name: "token", type: "core::starknet::contract_address::ContractAddress" },
      { name: "balance", type: "core::integer::u256" },
    ],
  },
  {
    type: "function",
    name: "get_balances",
    inputs: [
      { name: "address", type: "core::starknet::contract_address::ContractAddress" },
      { name: "tokens", type: "core::array::Span::<core::starknet::contract_address::ContractAddress>" },
    ],
    outputs: [{ type: "core::array::Span::<governance::balance_checker::NonZeroBalance>" }],
    state_mutability: "view",
  },
];

const balanceChecker = new Contract({
  abi: BALANCE_CHECKER_ABI,
  address: BALANCE_CHECKER_ADDRESS,
  providerOrAccount: provider,
});

// Query multiple tokens at once
const tokens = [
  "0x049d36570d4e46f48e99674bd3fcc84644ddd6b96f7c741b1562b82f9e004dc7", // ETH
  "0x04718f5a0fc34cc1af16a1cdee98ffb20c31f5cd61d6ab07201858f4287c938d", // STRK
  "0x033068f6539f8e6e6b131e6b2b814e6c34a5224bc66947c47dab9dfee93b35fb", // USDC
  "0x053c91253bc9682c04929ca02ed00b3e423f6710d2ee7e0d5ebb06f3ecf368a8", // USDC.e (legacy bridged USDC)
];

const result = await balanceChecker.get_balances(accountAddress, tokens);

// Parse response (only non-zero balances returned)
for (const item of result) {
  const tokenAddr = "0x" + BigInt(item.token).toString(16).padStart(64, "0");
  const balance = BigInt(item.balance); // starknet.js converts u256 to bigint
  console.log(`${tokenAddr}: ${balance}`);
}

When to use which:

• starknet_get_balance: Single token, simple use case
• starknet_get_balances: Multiple tokens, portfolio view, more efficient

Transfer Tokens

Use the starknet_transfer MCP tool with optional gasless mode:

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// Via MCP tool (recommended)
const result = await mcpClient.callTool({
  name: "starknet_transfer",
  arguments: {
    recipient: "0x...",
    token: "STRK",        // Symbol or contract address
    amount: "10.5",       // Human-readable amount
    gasfree: false,       // Optional: use paymaster
  }
});
// Returns: { transactionHash, recipient, token, amount, gasfree }

Gasless Transfer (Pay gas in token instead of ETH/STRK):

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// Pay gas in USDC instead of ETH/STRK
const result = await mcpClient.callTool({
  name: "starknet_transfer",
  arguments: {
    recipient: "0x...",
    token: "STRK",
    amount: "100",
    gasfree: true,
    gasToken: "USDC",    // Gas paid in USDC
  }
});

Direct starknet.js usage:

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import { Account, RpcProvider, CallData, cairo, ETransactionVersion } from "starknet";

const provider = new RpcProvider({ nodeUrl: process.env.STARKNET_RPC_URL });

const address = process.env.STARKNET_ACCOUNT_ADDRESS;
const privateKey = process.env.STARKNET_PRIVATE_KEY;
if (!address || !privateKey) throw new Error("Set STARKNET_ACCOUNT_ADDRESS and STARKNET_PRIVATE_KEY");

// starknet.js v10: Account uses an options object; provider calls go through account.provider
const account = new Account({
  provider,
  address,
  signer: privateKey,
  transactionVersion: ETransactionVersion.V3,
});

const tokenAddress = "0x04718f5a0fc34cc1af16a1cdee98ffb20c31f5cd61d6ab07201858f4287c938d"; // STRK

// Use cairo.uint256() instead of uint256.bnToUint256()
const { transaction_hash } = await account.execute({
  contractAddress: tokenAddress,
  entrypoint: "transfer",
  calldata: CallData.compile({
    recipient: recipientAddress,
    amount: cairo.uint256(amountInWei),
  }),
});
await account.provider.waitForTransaction(transaction_hash);

Estimate Fees

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const estimatedFee = await account.estimateInvokeFee({
  contractAddress: tokenAddress,
  entrypoint: "transfer",
  calldata: CallData.compile({
    recipient: recipientAddress,
    amount: cairo.uint256(amountInWei),
  }),
});
// estimatedFee.overall_fee -- total fee in STRK (V3 transactions)

Contract Interactions

Read contract state (view functions):

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// Via MCP tool
const result = await mcpClient.callTool({
  name: "starknet_call_contract",
  arguments: {
    contractAddress: "0x...",
    entrypoint: "balanceOf",
    calldata: [accountAddress],
  }
});

Write to contracts (state-changing functions):

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// Via MCP tool with gasless option
const result = await mcpClient.callTool({
  name: "starknet_invoke_contract",
  arguments: {
    contractAddress: "0x...",
    entrypoint: "approve",
    calldata: [spenderAddress, ...uint256Amount],
    gasfree: true,         // Optional: use paymaster
    gasToken: "USDC",      // Optional: pay gas in token
  }
});

Multi-Call (Batch Transactions)

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// Execute multiple operations in a single transaction
const { transaction_hash } = await account.execute([
  {
    contractAddress: tokenA,
    entrypoint: "approve",
    calldata: CallData.compile({
      spender: routerAddress,
      amount: cairo.uint256(amount),
    }),
  },
  {
    contractAddress: routerAddress,
    entrypoint: "swap",
    calldata: CallData.compile({ /* swap params */ }),
  },
]);

Gasless Transfer (Pay Gas in Token) - SDK v4 + PaymasterRpc

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import { getQuotes, executeSwap } from "@avnu/avnu-sdk";
import { PaymasterRpc } from "starknet";

// SDK v4: Use PaymasterRpc from starknet.js
// Mainnet: https://starknet.paymaster.avnu.fi
// Sepolia: https://sepolia.paymaster.avnu.fi
const paymaster = new PaymasterRpc({
  nodeUrl: process.env.AVNU_PAYMASTER_URL || "https://starknet.paymaster.avnu.fi",
});

// Any swap can be made gasless by adding paymaster option
const result = await executeSwap({
  provider: account,
  quote: bestQuote,
  slippage: 0.01,
  executeApprove: true,
  paymaster: {
    active: true,
    provider: paymaster,
    params: {
      version: "0x1",
      feeMode: {
        mode: "default",
        gasToken: usdcAddress, // Pay gas in USDC instead of ETH/STRK
      },
    },
  },
});

Token Resolution

The MCP server uses TokenService to resolve token symbols and addresses. Static tokens (ETH, STRK, USDC, USDT) are always available. For other tokens, the service fetches metadata from avnu SDK.

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import { fetchTokenByAddress, fetchTokens, fetchVerifiedTokenBySymbol } from '@avnu/avnu-sdk';

// Get token by symbol (undefined if not a verified/unruggable token)
const lords = await fetchVerifiedTokenBySymbol('LORDS');
if (!lords) throw new Error('LORDS not found in avnu token list');
console.log(lords.address, lords.decimals); // 0x0124aeb..., 18

// Get token by address (any token)
const token = await fetchTokenByAddress('0x...');
console.log(token.symbol, token.name, token.decimals);

// Get verified tokens (returns Page<Token>; tokens are in `content`)
const page = await fetchTokens({ tags: ['Verified'], size: 100 });
page.content.forEach(t => console.log(t.symbol, t.address));

Static tokens available without network calls: ETH, STRK, USDC, USDT

Session Keys (Agent Autonomy)

Session keys allow agents to execute pre-approved transactions without per-action human approval:

1. Human owner creates a session key with policies:
   • Allowed contract addresses and methods
   • Maximum spending per transaction/period
   • Expiry timestamp
2. Agent uses the session key for autonomous operations
3. Owner can revoke at any time

Reference implementation: Cartridge Controller

Configuration

Error Handling

References

• starknet.js Documentation
• Starknet Account Abstraction
• Session Keys Guide
• avnu Paymaster