Grok 4.1 Fast and Agent Tools API

2025-11-19 · Publisher : xAI · Domain : Artificial Intelligence

xAI launches Grok 4.1 Fast, its best tool-calling model with 2 million tokens of context, and the Agent Tools API for building autonomous agents with server-side tools.

What changes

  • Grok 4.1 Fast trained with reinforcement learning in simulated environments covering dozens of domains, for customer support and finance.
  • Performance announced as stable across the entire 2-million-token window in multi-turn use.
  • Hallucination rate halved compared with Grok 4 Fast (FActScore), according to xAI.
  • Agent Tools API: web and X search, code execution, file search, MCP tools, executed on xAI infrastructure.

### Specifications - Context: 2 million tokens. - API identifiers: grok-4-1-fast-reasoning and grok-4-1-fast-non-reasoning. - Availability: xAI API (console.x.ai); the Enterprise API is mentioned in the release notes. Knowledge cutoff: not disclosed. ### Pricing Per million tokens, in USD. | Input | Cached input | Output | |---|---|---| | $0.20 | $0.05 | $0.50 | Tool calls from $5 per 1,000 successful calls (a cut of up to 50% in tool prices announced in the release notes). ### Benchmarks Scores published by the vendor. | Benchmark | Score | |---|---| | τ²-bench Telecom | 100% | | Berkeley Function Calling v4 (overall accuracy) | 72% | | Research-Eval Reka (with Agent Tools API) | 63.9 | | FRAMES | 87.6 | | X Browse (internal benchmark) | 56.3 | ### Key takeaways An offering geared toward enterprise agents: inexpensive model, long context and tools managed on the xAI side.

Links

Tags : LLM, xAI, Grok, Grok 4.1 Fast, Agents, API