# Best Practices

## **Security**

### **Input Validation**

```javascript
Utils.assert(Utils.addressCheck(to), 'Invalid address');
Utils.assert(Utils.stoI256Check(amount), 'Invalid amount');
Utils.assert(Utils.int256Compare(amount, '0') > 0, 'Amount must be positive');
```

### **Access Control**

```javascript
const owner = Chain.load('owner');
Utils.assert(Chain.msg.sender === owner, 'Only owner');
```

### **Reentrancy Protection**

```javascript
Utils.assert(!Chain.load('locked'), 'Reentrant call');
Chain.store('locked', 'true');
// ... operations ...
Chain.store('locked', 'false');
```

***

## **Gas Optimization**

### **Minimize Storage**

```javascript
// Bad: Multiple stores
Chain.store('data1', value1);
Chain.store('data2', value2);

// Good: Single combined store
const data = JSON.stringify({data1: value1, data2: value2});
Chain.store('combined', data);
```

### **Use Local Variables**

```javascript
// Bad: Multiple loads
if (Chain.load('balance_' + addr) > amount) {
    Chain.store('balance_' + addr, Chain.load('balance_' + addr) - amount);
}

// Good: Load once
const balance = Chain.load('balance_' + addr);
if (balance > amount) {
    Chain.store('balance_' + addr, balance - amount);
}
```

***

## **Code Organization**

### **Separate Concerns**

```javascript
// Storage layer
const Storage = function() {
    const self = this;
    self.get = function(key) { return Chain.load(key); };
    self.set = function(key, val) { Chain.store(key, val); };
};

// Business logic layer
const Logic = function() {
    const self = this;
    const storage = new Storage();
    // ... use storage
};
```

### **Clear Error Messages**

```javascript
Utils.assert(condition, 'Clear error message explaining what went wrong');
```

### **Event Logging**

```javascript
// Always log important state changes
Chain.tlog('StateChanged', oldValue, newValue, timestamp);
```

***


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://docs.zetrix.com/en/developer-resources/zetrix-mcp-server/smart-contract-development/best-practices.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.