> ## Documentation Index > Fetch the complete documentation index at: https://docs.siray.ai/llms.txt > Use this file to discover all available pages before exploring further. # Grok 4 Fast Reasoning > xAI's Grok 4 Fast Reasoning is a cost-efficient LLM with a 2M context, offering deep, step-by-step reasoning and native tool use for complex problem-solving. ### Model Use Cases A cost-efficient LLM with a 2M context window. It offers deep, step-by-step reasoning and native tool use for complex problem-solving at a low cost. ### Key Features * **2M Context:** Provides a massive context window for entire codebases or extremely long documents. * **Cost Efficiency:** Offers near-flagship reasoning power at a highly optimized price point. * **Native Tool Use:** Integrates web browsing and tool use for accurate, current, and verifiable answers.