HTS System Contract Skill

Hedera Token Service (HTS) System Contract

HTS precompile at 0x167 enables Solidity contracts to create and manage Hedera-native tokens with built-in compliance controls (KYC, freeze, pause) and custom fees.

Quick Reference

Imports:

import {HederaTokenService} from "@hashgraph/smart-contracts/contracts/system-contracts/hedera-token-service/HederaTokenService.sol";
import {KeyHelper} from "@hashgraph/smart-contracts/contracts/system-contracts/hedera-token-service/KeyHelper.sol";
import {ExpiryHelper} from "@hashgraph/smart-contracts/contracts/system-contracts/hedera-token-service/ExpiryHelper.sol";
import {HederaResponseCodes} from "@hashgraph/smart-contracts/contracts/system-contracts/hedera-token-service/HederaResponseCodes.sol";

Safe variants (auto-revert on failure): SafeHTS.sol, SafeViewHTS.sol

Critical: HBAR Payment Required

Token creation requires explicit HBAR value payment (not just gas):

// ❌ WRONG - fails with INSUFFICIENT_TX_FEE
(int rc, address token) = createNonFungibleToken(token);

// ✅ CORRECT
(int rc, address token) = createNonFungibleToken{value: msg.value}(token);

Call from TypeScript:

await contract.createToken(name, symbol, {
  gasLimit: 350_000,
  value: ethers.parseEther("15"), // ~$1-2 USD of HBAR
});

Token Key System

Seven key types control token operations (bit positions for keyType field):

Key	Bit	Value	Controls
ADMIN	0	1	Update token, keys, deletion
KYC	1	2	Grant/revoke KYC
FREEZE	2	4	Freeze/unfreeze accounts
WIPE	3	8	Wipe balances
SUPPLY	4	16	Mint/burn
FEE	5	32	Update fees
PAUSE	6	64	Pause all operations

Use KeyHelper for key construction:

keys[0] = getSingleKey(KeyType.SUPPLY, KeyValueType.CONTRACT_ID, address(this));

See references/keys.md for key value types and JSON tuple format.

Association Model

Accounts must associate with tokens before receiving them:

int rc = associateToken(accountAddress, tokenAddress);
require(
    rc == HederaResponseCodes.SUCCESS ||
    rc == HederaResponseCodes.TOKEN_ALREADY_ASSOCIATED_TO_ACCOUNT,
    "Association failed"
);

Common Patterns

Fungible Token Creation

function createToken() external payable {
    IHederaTokenService.HederaToken memory token;
    token.name = "My Token";
    token.symbol = "MTK";
    token.treasury = address(this);
    token.expiry = createAutoRenewExpiry(address(this), 7776000); // 90 days

    (int rc, address created) = createFungibleToken{value: msg.value}(
        token, 1000000, 18  // initialSupply, decimals
    );
    require(rc == HederaResponseCodes.SUCCESS, "Create failed");
}

Mintable NFT Collection

function createNFT() external payable {
    IHederaTokenService.HederaToken memory token;
    token.name = "My NFT";
    token.symbol = "MNFT";
    token.treasury = address(this);
    token.tokenSupplyType = true;  // FINITE
    token.maxSupply = 10000;

    IHederaTokenService.TokenKey[] memory keys = new IHederaTokenService.TokenKey[](1);
    keys[0] = getSingleKey(KeyType.SUPPLY, KeyValueType.CONTRACT_ID, address(this));
    token.tokenKeys = keys;
    token.expiry = createAutoRenewExpiry(address(this), 7776000);

    (int rc, address created) = createNonFungibleToken{value: msg.value}(token);
    require(rc == HederaResponseCodes.SUCCESS, "Create failed");
}

function mintNFT(bytes memory metadata) external {
    bytes[] memory metas = new bytes[](1);
    metas[0] = metadata;
    (int rc, , int64[] memory serials) = mintToken(tokenAddress, 0, metas);
    require(rc == HederaResponseCodes.SUCCESS, "Mint failed");
}

KYC-Enabled Token

Treasury must self-grant KYC after creation:

// After token creation with KYC key
int kycRc = grantTokenKyc(tokenAddress, address(this));
require(kycRc == HederaResponseCodes.SUCCESS, "Self-KYC failed");

Response Code Handling

Always check response codes. SUCCESS = 22.

require(responseCode == HederaResponseCodes.SUCCESS, "Operation failed");

Common codes: See references/response-codes.md

Additional References

• API Reference: references/api.md - All function signatures
• Custom Fees: references/fees.md - Fixed, fractional, royalty fees
• Compliance Controls: references/compliance.md - KYC, freeze, pause details
• Struct Definitions: references/structs.md - HederaToken, Expiry, etc.
• Troubleshooting: references/troubleshooting.md - Common errors and fixes