> ## Documentation Index
> Fetch the complete documentation index at: https://docs.mycelium.sh/llms.txt
> Use this file to discover all available pages before exploring further.

# Use paymaster

To use paymaster you simply need to pass a ERC-20 token that you want a user to pay a gas with

Currently paymaster is integrated to several operations with the SDK:

1. Send a transaction
2. Deposit funds to a DeFi opportunity (`earn()` method)
3. Withdraw funds to a DeFi opportunity (`withdraw()` method)

## How to use a paymaster?

Here is a quick exmaple how to sponsor gas during the depositing a user funds to DeFi opportunity

<Steps>
  <Step title="Init SDK">
    ```javascript theme={null}
    import { MyceliumSDK } from '@mycelium-sdk/core';


    const sdk = await MyceliumSDK.init({
        apiKey:
          "sk_e010bc44958665229cb89634448f81f532231ce131c4eb98816eadcb2e6ed7fa47",
        chainId: 8453,
        protocolsSecurityConfig: {
          riskLevel: "low",
        },
      });
    ```
  </Step>

  <Step title="Get a vault to depoist">
    ```javascript theme={null}
    const vaults = await sdk.protocols.getBestVaults()
    ```
  </Step>

  <Step title="Get or create a user wallet">
    ```javascript theme={null}
    const wallet = await this.sdk.wallet.createAccount()
    ```
  </Step>

  <Step title="Deposit using paymaster">
    <Warning>
      Make sure that the smart wallet have enough token balance that you pass to paymaster for gas sponsoring

      If the gas token will be the same token that you're depositing, you need to check that a user will leave at leas small portion on the wallet to complete the deposit AND make a withdrawal later on

      Check more exmples of this use case below
    </Warning>

    ```javascript theme={null}
    const USDC_TOKEN_ADDRESS = "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913"

    const txnHash = await wallet.earn(
    	selectedVault.vaultInfo, 
    	amountToDeposit, 
    	{
          paymasterToken: USDC_TOKEN_ADDRESS,
        }
    );
    ```
  </Step>
</Steps>

## Reserved gas amount

In some cases you want to use for gas sponsring the same ERC-20 token that you're using for a deposit to a DeFi opportunity

For example, you want to deposit 100 USDC to a vault. In this case, you need to care that a user will still have some small portion of USDC on the smart wallet to perform the deposit action as well as withdrawal later on

In case of L2 networks, the gas price will be small on 0.01 USDC should be enough to cover 1 operation with gas sponsoring

For some L1 networks (e.g. Ethereum) gas can be significantly higher and you need to care that user would have enought ERC-20 token to cover the gas fee

The same will be with ERC-20 tokens with decimals > 6, e.g. ETH or BTC. In this case, you can reserve at least 1% of the token for the further gas fee, so a user can successfully complete onchain operations