Gemini 3.1 Pro Preview Custom Tools vs Grok Build 0.1
Gemini 3.1 Pro Preview Custom Tools (2026) and Grok Build 0.1 (2026) are agentic coding models from Google DeepMind and xAI. Gemini 3.1 Pro Preview Custom Tools ships a 1M-token context window, while Grok Build 0.1 ships a 256K-token context window. On pricing, Grok Build 0.1 costs $1/1M input tokens versus $2/1M for the alternative. This comparison covers specs, pricing, capabilities, benchmarks, provider availability, and production fit.
Grok Build 0.1 is ~100% cheaper at $1/1M; pay for Gemini 3.1 Pro Preview Custom Tools only for long-context analysis.
Decision scorecard
Local evidence first| Signal | Gemini 3.1 Pro Preview Custom Tools | Grok Build 0.1 |
|---|---|---|
| Decision fit | RAG, Long context, and Classification | Coding, RAG, and Agents |
| Context window | 1M | 256K |
| Cheapest output | $12/1M tokens | $2/1M tokens |
| Provider routes | 1 tracked | 1 tracked |
| Shared benchmarks | 0 rows | 0 rows |
Decision tradeoffs
- Gemini 3.1 Pro Preview Custom Tools has the larger context window for long prompts, retrieval packs, or transcript analysis.
- Local decision data tags Gemini 3.1 Pro Preview Custom Tools for RAG, Long context, and Classification.
- Grok Build 0.1 has the lower cheapest tracked output price at $2/1M tokens.
- Grok Build 0.1 uniquely exposes Reasoning, Function calling, and Tool use in local model data.
- Local decision data tags Grok Build 0.1 for Coding, RAG, and Agents.
Monthly cost at traffic
Estimate token spend from the cheapest tracked input and output prices on this page.
Gemini 3.1 Pro Preview Custom Tools
$4,600
Cheapest tracked route: OpenRouter
Grok Build 0.1
$1,300
Cheapest tracked route: xAI Console
Estimated monthly gap: $3,300. Batch, cache, and negotiated pricing are excluded from this local estimate.
Switch friction
- No overlapping tracked provider route is sourced for Gemini 3.1 Pro Preview Custom Tools and Grok Build 0.1; plan for SDK, billing, or endpoint changes.
- Grok Build 0.1 is $10/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
- Grok Build 0.1 adds Reasoning, Function calling, and Tool use in local capability data.
- No overlapping tracked provider route is sourced for Grok Build 0.1 and Gemini 3.1 Pro Preview Custom Tools; plan for SDK, billing, or endpoint changes.
- Gemini 3.1 Pro Preview Custom Tools is $10/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
- Check replacement coverage for Reasoning, Function calling, and Tool use before moving production traffic.
Specs
| Specification | ||
|---|---|---|
| Released | 2026-01-01 | 2026-05-14 |
| Context window | 1M | 256K |
| Parameters | — | — |
| Architecture | decoder only | - |
| License | Unknown | Proprietary |
| Knowledge cutoff | 2025-01 | - |
Pricing and availability
| Pricing attribute | Gemini 3.1 Pro Preview Custom Tools | Grok Build 0.1 |
|---|---|---|
| Input price | $2/1M tokens | $1/1M tokens |
| Output price | $12/1M tokens | $2/1M tokens |
| Providers |
Capabilities
| Capability | Gemini 3.1 Pro Preview Custom Tools | Grok Build 0.1 |
|---|---|---|
| Vision | No | No |
| Multimodal | No | No |
| Reasoning | No | Yes |
| Function calling | No | Yes |
| Tool use | No | Yes |
| Structured outputs | Yes | Yes |
| Code execution | No | No |
Benchmarks
No shared benchmark rows are currently sourced for this pair.
Deep dive
The capability footprint differs most on reasoning mode: Grok Build 0.1, function calling: Grok Build 0.1, and tool use: Grok Build 0.1. Both models share structured outputs, so the practical split is not just feature count. Use those differences to decide whether the page is about raw model quality, agentic coding support, multimodal ingestion, or predictable structured API behavior.
For cost, Gemini 3.1 Pro Preview Custom Tools lists $2/1M input and $12/1M output tokens, while Grok Build 0.1 lists $1/1M input and $2/1M output tokens on the cheapest tracked provider. A 70/30 input-output blend puts Grok Build 0.1 lower by about $3.7 per million blended tokens. Availability is 1 providers versus 1, so concentration risk also matters.
Choose Gemini 3.1 Pro Preview Custom Tools when long-context analysis and larger context windows are central to the workload. Choose Grok Build 0.1 when coding workflow support and lower input-token cost are more important. For production, rerun your own prompts through the exact provider, region, and tool stack you plan to ship. This keeps the decision grounded in measurable tradeoffs instead of brand-level assumptions.
FAQ
Which has a larger context window, Gemini 3.1 Pro Preview Custom Tools or Grok Build 0.1?
Gemini 3.1 Pro Preview Custom Tools supports 1M tokens, while Grok Build 0.1 supports 256K tokens. That gap matters most for long documents, large codebases, retrieval-heavy agents, and conversations where earlier context must remain visible.
Which is cheaper, Gemini 3.1 Pro Preview Custom Tools or Grok Build 0.1?
Grok Build 0.1 is cheaper on tracked token pricing. Gemini 3.1 Pro Preview Custom Tools costs $2/1M input and $12/1M output tokens. Grok Build 0.1 costs $1/1M input and $2/1M output tokens. Provider discounts or batch pricing can still change the final bill.
Is Gemini 3.1 Pro Preview Custom Tools or Grok Build 0.1 open source?
Gemini 3.1 Pro Preview Custom Tools is listed under Unknown. Grok Build 0.1 is listed under Proprietary. License labels affect whether you can self-host, redistribute weights, or rely only on hosted APIs, so confirm the upstream license before deployment.
Which is better for reasoning mode, Gemini 3.1 Pro Preview Custom Tools or Grok Build 0.1?
Grok Build 0.1 has the clearer documented reasoning mode signal in this comparison. If reasoning mode is mission-critical, validate it against the provider endpoint because model-level support and API-level exposure can differ.
Which is better for function calling, Gemini 3.1 Pro Preview Custom Tools or Grok Build 0.1?
Grok Build 0.1 has the clearer documented function calling signal in this comparison. If function calling is mission-critical, validate it against the provider endpoint because model-level support and API-level exposure can differ.
Where can I run Gemini 3.1 Pro Preview Custom Tools and Grok Build 0.1?
Gemini 3.1 Pro Preview Custom Tools is available on OpenRouter. Grok Build 0.1 is available on xAI Console. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
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Last reviewed: 2026-05-20. Data sourced from public model cards and provider documentation.