> For the complete documentation index, see [llms.txt](https://docs-sdk.crypto-chief.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs-sdk.crypto-chief.com/processing/kotlin/guides/contract-calls.md).

# Contract calls (EVM / TRON)

Call EVM, TRON, and Solana contracts in Kotlin without hand-encoding calldata.

Most real-world transactions are smart-contract calls. You never encode the `data` field by hand: give the SDK a typed description and get back a signed reservation.

{% hint style="warning" %}
Contract-type transactions (`signEvmCall`, `erc20Transfer`, `signTronCall`, `signAnchorCall` — every helper in this guide signs `type=contract`) are covered by the same [execute-time pre-flight](/processing/kotlin/guides/sign-execute.md): a wallet without enough native coin for gas gets `PREFLIGHT_FAILED` instead of an on-chain revert or a silent gas burn. On TRON, the call is additionally simulated, so a reverting call (including an insufficient token balance) is rejected as `simulation_reverted` before any fee is spent.
{% endhint %}

## EVM — by Solidity signature

{% hint style="danger" %}
This snippet shows the **encoder**, not a complete swap. Two things have to be true before a swap like this succeeds on chain:

* **An allowance.** Uniswap's router moves your input token with `transferFrom`, so it needs an ERC-20 `approve(address,uint256)` on that token first, confirmed before the swap is signed — the nonce comes from chain state. Without it the swap reverts and burns the gas.
* **A slippage floor.** `amountOutMin` of `0` accepts whatever the pool returns, which on a public mempool hands the trade to the first sandwich bot that sees it. Pass a real minimum, in the output token's base units.
  {% endhint %}

```kotlin
import com.cryptochief.processing.Amount
import com.cryptochief.processing.Chain

val amountIn  = Amount.toBase("0.01", 18)
val amountMin = java.math.BigInteger.ZERO

val signed = client.transactions.signEvmCall(
    network     = Chain.ETH_MAINNET,
    fromAddress = "0xYourWallet...",
    contract    = "0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D", // Uniswap V2 router
    method      = "swapExactTokensForTokens(uint256,uint256,address[],address,uint256)",
    args        = listOf(amountIn, amountMin, listOf(tokenIn, tokenOut), "0xYou...", deadline),
    urlCallback = "https://your.app/webhooks/transaction",
)
```

The encoder supports `uint/int<M>`, `address`, `bool`, `bytes`, `bytes<N>`, `string`, and fixed/dynamic arrays of those. Argument values accept `BigInteger`, plain Kotlin ints/longs, decimal/hex strings, `ByteArray`, and `List<*>`.

## ERC-20 / TRC-20 transfer (one-liner)

```kotlin
val amount = Amount.toBase("12.5", 6) // USDT has 6 decimals

client.transactions.erc20Transfer(
    network       = Chain.ETH_MAINNET,
    fromAddress   = "0xYourWallet...",
    tokenContract = "0xdAC17F958D2ee523a2206206994597C13D831ec7",
    recipient     = "0xRecipient...",
    amount        = amount,
)
```

## TRON — same encoder, base58 addresses

`signTronCall` (an alias of `signEvmCall`) accepts both base58 (`T...`) and `0x41`-prefixed hex addresses:

```kotlin
client.transactions.signTronCall(
    network     = Chain.TRON_MAINNET,
    fromAddress = "TYourWallet...",
    contract    = "TR7NHqjeKQxGTCi8q8ZY4pL8otSzgjLj6t", // USDT TRC-20
    method      = "transfer(address,uint256)",
    args        = listOf("TRecipient...", amount),
)
```

## Solana — Anchor program

```kotlin
import com.cryptochief.processing.models.SolanaAccount
import com.cryptochief.processing.solana.Borsh

val signed = client.transactions.signAnchorCall(
    network     = Chain.SOLANA_MAINNET,
    fromAddress = "YourWallet...",
    program     = "YourProgramId...",
    method      = "initialize",
    args        = listOf(
        Borsh.u64(1_000_000L),
        Borsh.string("hello"),
    ),
    accounts    = listOf(
        SolanaAccount(pubkey = "YourWallet...", isSigner = true, isWritable = true),
    ),
)
```

For non-Anchor Solana programs, use `signSolanaCall` with raw instruction bytes. For TON contracts, see [TON transfers](/processing/kotlin/guides/ton.md).