xAI

xAI develops Grok, a family of large language models designed for reasoning, coding, and multimodal understanding. The model lineup includes Grok 4 for frontier reasoning, Grok 4.1 Fast for cost-efficient tool calling with 2M token context windows, and Grok 3 variants for enterprise workloads. Models support text and image input, with specialized versions for image generation and code. A key differentiator is native integration with X (formerly Twitter), enabling real-time access to posts, trends, and conversations through built-in X Search tools.

The API includes server-side tools for web search, X search, code execution, and document search that models can invoke autonomously. Grok models are trained on xAI's Colossus supercomputer cluster. The API is compatible with OpenAI SDKs, supporting REST, gRPC, and Python integrations for straightforward migration. Regional endpoints in the US and EU address data residency requirements. Automatic prompt caching reduces costs for repeated queries. Pricing starts at $0.20 per million input tokens for Grok 4.1 Fast models, with tool invocations billed separately at $5 per 1,000 calls.

Vapi and xAI together enable voice AI applications powered by Grok's reasoning and real-time knowledge capabilities. xAI provides the language models that can drive intelligent voice conversations with access to current information through native web and X search integration. This combination allows developers to build voice agents that can answer questions about breaking news, trending topics, and real-time events by querying X's data stream directly. Grok's large context windows support extended conversations with full history retention, while its reasoning capabilities handle complex multi-step queries. The built-in code execution tool enables voice agents to perform calculations, data analysis, and dynamic problem-solving during calls.

For applications requiring current awareness—customer support about recent product launches, financial services discussing market movements, or media monitoring—xAI's real-time search tools eliminate the need for separate retrieval infrastructure. The API's OpenAI compatibility simplifies integration, and competitive token pricing makes high-volume voice applications economically viable.