# Frequently Asked Questions
## API Billing FAQ
### How am I charged for API usage?
You are charged based on token consumption:
- **Prompt tokens**: Input text tokens
- **Completion tokens**: Generated output tokens
- **Reasoning tokens**: Tokens used for model reasoning
- **Image tokens**: Tokens for image processing
- **Audio tokens**: Tokens for audio processing
- **Cached tokens**: Previously processed tokens (discounted rate)
### What payment methods are accepted?
- Credit/debit cards
- Prepaid credits
- Monthly invoiced billing (for eligible accounts)
### How do prepaid credits work?
- Pre-purchase credits for your team
- API consumption is deducted from available credits
- No overage charges until credits are exhausted
- Credits don't expire
### How does monthly invoiced billing work?
- xAI generates a monthly invoice based on API consumption
- Used when prepaid credits are not available
- Billed at the end of each billing period
### Where can I see my usage?
Use the Usage Explorer in the xAI Console to:
- View real-time usage
- See historical data
- Compare usage across API keys
- Track costs by model
### How do I get a higher rate limit?
Email support@x.ai with:
- Your account information
- Anticipated volume
- Use case description
## Grok Website/Apps FAQ
### Is the xAI API separate from the Grok website?
Yes. X Premium purchases won't affect your service status on xAI API, and vice versa. These are separate offerings.
### Can I use my X Premium subscription for API access?
No, API access requires a separate xAI API account and API key.
## Technical FAQ
### What is the knowledge cutoff date?
The knowledge cutoff date for Grok 3 and Grok 4 is **November 2024**.
### How do I get real-time information?
Enable server-side search tools:
- `web_search` - Search the web
- `x_keyword_search` - Search X posts
- `x_semantic_search` - Semantic X search
### Which models support function calling?
All Grok models support function calling:
- grok-4 (recommended)
- grok-4-fast
- grok-4-1-fast-reasoning
- grok-4-1-fast-non-reasoning
- grok-code-fast-1
- grok-3
### What image formats are supported?
Supported formats for image understanding:
- JPEG/JPG
- PNG
### What are the context length limits?
| Model | Context Length |
|-------|----------------|
| grok-4 | 2,000,000 tokens |
| grok-4-fast | 131,072 tokens |
| grok-code-fast-1 | 256,000 tokens |
| grok-3 | 131,072 tokens |
### Are there rate limits?
Yes. Rate limits vary by tier and include:
- Requests per minute (RPM)
- Tokens per minute (TPM)
Error code 429 indicates rate limit exceeded.
### How do I handle rate limit errors?
Implement exponential backoff:
```python
import time
def make_request_with_retry(func, max_retries=5):
for attempt in range(max_retries):
try:
return func()
except Exception as e:
if "429" in str(e):
wait = 2 ** attempt
time.sleep(wait)
else:
raise
```
### What parameters are not supported by reasoning models?
Grok 4 (reasoning model) does not support:
- `presencePenalty`
- `frequencyPenalty`
- `stop`
- `reasoning_effort`
Adding these will result in an error.
### Is there a batch API?
The xAI API does not currently offer a dedicated batch API. Use async requests for high-volume processing.
### How do I check service status?
- Status page: https://status.x.ai
- RSS feed: https://status.x.ai/feed.xml
## SDK FAQ
### Which SDK should I use?
| SDK | When to Use |
|-----|-------------|
| xAI SDK | Full feature access, all products |
| OpenAI SDK | Easy migration, familiar API |
| Anthropic SDK | Anthropic-style requests |
### What xAI SDK version do I need?
| Feature | Minimum Version |
|---------|-----------------|
| Agentic tool calling | 1.3.1 |
| Files API | 1.4.0 |
| Inline citations | 1.5.0 |
| Location-based search | 1.6.0 |
### Is the API compatible with OpenAI's SDK?
Yes, the xAI API is fully compatible with the OpenAI SDK. Just change the base URL:
```python
from openai import OpenAI
client = OpenAI(
api_key="your-xai-api-key",
base_url="https://api.x.ai/v1"
)
```
