[xAI Releases Grok 4.1 Fast Model and Agent Tools API] xAI has announced the launch of its next-generation model, Grok 4.1 Fast, along with the simultaneous release of the Agent Tools API. Grok 4.1 Fast features a 2-million-token context window, optimized for practical applications such as customer support and in-depth research. It supports tool invocation, code execution, web browsing, and other functionalities, and has been trained in multi-domain environments using long-term reinforcement learning. The model is now available via the xAI API, priced at $0.2 per million tokens for input and $0.5 for output. It will also be available for free trial on the OpenRouter platform over the next two weeks.