$ cat wiki/models/grok-4-1-fast.md
Grok 4.1 Fast (xAI)
Spec
| Attribute | Value |
|---|---|
| Developer | xAI |
| Released | 2026-05 (exact day unconfirmed) |
| Announced | 2026-05 (exact day unconfirmed) |
| Context window | 2M tokens |
| Pricing | $0.20/M input · $0.50/M output |
| License | unknown |
| Availability | xAI API (with managed Agent Tools API) |
| Specialty | Tool-calling, agentic tasks, customer support, finance |
Release Date
- May 2026 (exact date unconfirmed; live on x.ai/api as of May 2026)
Benchmarks
- Hallucination rate: 50% lower than Grok 4 Fast (FActScore)
- Factuality: On par with Grok 4 overall despite its speed advantage
- Described as xAI's "best tool-calling model"
Agent Tools API (Bundled)
New managed tool infrastructure requiring minimal developer setup:
| Tool | Description |
|---|---|
| Web browsing | Real-time web search |
| X post search | Live Twitter/X data (xAI data moat) |
| Code execution | Sandboxed runner |
| Document retrieval | Upload + query documents |
| All tools run on xAI infrastructure — developers don't manage API keys, rate limits, sandboxes, or retrieval pipelines. |
Use Cases
- Production-grade agents specializing in tool-calling and agentic search
- Customer support agents with live web + X data
- Finance workflows with real-time market information
- Document Q&A agents
Compared To
| Model | Context | Agent Tools | Hallucination | Price (per 1M in/out) |
|---|---|---|---|---|
| Grok 4.1 Fast | 2M | Managed (web, X, code, docs) | −50% vs Grok 4 Fast | $0.20/$0.50 |
| Claude Opus 4.7 | 200K | MCP ecosystem | — | $15/$75 |
| GPT-Realtime-2 | 128K | Tool calls | — | — |
| Gemini 3.5 Flash | 1M | MCP Atlas 83.6% | — | — |
Significance
- xAI's managed Agent Tools API is a direct response to Anthropic's MCP ecosystem and OpenAI's tool-call infrastructure
- The X post search tool is a genuine data moat — no other frontier provider has real-time Twitter/X access built in
- $0.20/$0.50 pricing makes it one of the cheapest frontier-tier agentic APIs in May 2026
- The 2M context window enables very long document and conversation agentic workflows
Open Questions
- How does X post search quality compare to real-time Perplexity/web search?
- Will the Agent Tools API expand to include more platform integrations (GitHub, Notion, etc.)?
- What is its relationship to Grok Connectors (the deep integration launched 2026-05-06)?
Sources
- (source)
Related
- xAI
- Grok Build — terminal CLI agentic coding product
- Agents (LLM Agents) — agentic tool-use