Gemini 3.1 Pro Preview Custom Tools vs Grok 4.20
Gemini 3.1 Pro Preview Custom Tools (2026) and Grok 4.20 (2026) are frontier reasoning models from Google DeepMind and xAI. Gemini 3.1 Pro Preview Custom Tools ships a 1m-token context window, while Grok 4.20 ships a 1m-token context window. On pricing, Grok 4.20 costs $1.25/1M input tokens versus $2/1M for the alternative. This comparison covers specs, pricing, API access, capabilities, benchmarks, input and output token costs, and production fit for coding and agent workloads.
Grok 4.20 is ~60% cheaper at $1.25/1M; pay for Gemini 3.1 Pro Preview Custom Tools only for provider fit.
Decision scorecard
Local evidence first| Signal | Gemini 3.1 Pro Preview Custom Tools | Grok 4.20 |
|---|---|---|
| Best for | long-context analysis | reasoning-heavy apps, multimodal apps, and tool-calling agents |
| Decision fit | RAG, Long context, and Classification | Coding, RAG, and Agents |
| Context window | 1m | 1m |
| Cheapest output | $12/1M tokens | $2.50/1M tokens |
| Provider routes | 1 tracked | 2 tracked |
| Shared benchmarks | 0 rows | 0 rows |
Decision tradeoffs
- Local decision data tags Gemini 3.1 Pro Preview Custom Tools for RAG, Long context, and Classification.
- Grok 4.20 has the lower cheapest tracked output price at $2.50/1M tokens.
- Grok 4.20 has broader tracked provider coverage for fallback and procurement flexibility.
- Grok 4.20 uniquely exposes Vision, Multimodal, and Reasoning in local model data.
- Local decision data tags Grok 4.20 for Coding, RAG, and Agents.
Monthly cost at traffic
Estimate token spend from the cheapest tracked input and output route or tier on this page.
Gemini 3.1 Pro Preview Custom Tools
$4,600
Cheapest tracked route/tier: OpenRouter
Grok 4.20
$1,625
Cheapest tracked route/tier: xAI Console
Estimated monthly gap: $2,975. Batch, cache, alternate speed tiers, and negotiated pricing are excluded from this local estimate.
Switch friction
- Provider overlap exists on OpenRouter; start route-level A/B tests there.
- Grok 4.20 is $9.50/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
- Grok 4.20 adds Vision, Multimodal, and Reasoning in local capability data.
- Provider overlap exists on OpenRouter; start route-level A/B tests there.
- Gemini 3.1 Pro Preview Custom Tools is $9.50/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
- Check replacement coverage for Vision, Multimodal, and Reasoning before moving production traffic.
Specs
| Specification | ||
|---|---|---|
| Released | 2026-01-01 | 2026-02-17 |
| Context window | 1m | 1m |
| Parameters | — | — |
| Architecture | decoder only | - |
| License | Proprietary | Proprietary |
| Knowledge cutoff | 2025-01 | 2024-11 |
Pricing and availability
| Pricing attribute | Gemini 3.1 Pro Preview Custom Tools | Grok 4.20 |
|---|---|---|
| Input price | $2/1M tokens | $1.25/1M tokens |
| Output price | $12/1M tokens | $2.50/1M tokens |
| Providers |
Capabilities
| Capability | Gemini 3.1 Pro Preview Custom Tools | Grok 4.20 |
|---|---|---|
| Vision | No | Yes |
| Multimodal | No | Yes |
| Reasoning | No | Yes |
| Function calling | No | Yes |
| Tool use | No | Yes |
| Structured outputs | Yes | Yes |
| Code execution | No | No |
| IDE integration | No | No |
| Computer use | No | No |
| Parallel agents | No | No |
Benchmarks
No shared benchmark rows are currently sourced for this pair.
Deep dive
The capability footprint differs most on vision: Grok 4.20, multimodal input: Grok 4.20, reasoning mode: Grok 4.20, function calling: Grok 4.20, and tool use: Grok 4.20. 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 on the cheapest tracked provider, while Grok 4.20 lists $1.25/1M input and $2.50/1M output tokens on the cheapest tracked provider. A 70/30 input-output blend puts Grok 4.20 lower by about $3.38 per million blended tokens. Availability is 1 providers versus 2, so concentration risk also matters.
Choose Gemini 3.1 Pro Preview Custom Tools when provider fit are central to the workload. Choose Grok 4.20 when reasoning depth, lower input-token cost, and broader provider choice 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 4.20?
Gemini 3.1 Pro Preview Custom Tools supports 1m tokens, while Grok 4.20 supports 1m 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 4.20?
Grok 4.20 is cheaper on tracked token pricing. Gemini 3.1 Pro Preview Custom Tools costs $2/1M input and $12/1M output tokens. Grok 4.20 costs $1.25/1M input and $2.50/1M output tokens. Provider discounts or batch pricing can still change the final bill.
Is Gemini 3.1 Pro Preview Custom Tools or Grok 4.20 open source?
Gemini 3.1 Pro Preview Custom Tools is listed under Proprietary. Grok 4.20 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 vision, Gemini 3.1 Pro Preview Custom Tools or Grok 4.20?
Grok 4.20 has the clearer documented vision signal in this comparison. If vision is mission-critical, validate it against the provider endpoint because model-level support and API-level exposure can differ. Use this as a quick comparison signal, then confirm the provider-specific limits before committing to production.
Which is better for multimodal input, Gemini 3.1 Pro Preview Custom Tools or Grok 4.20?
Grok 4.20 has the clearer documented multimodal input signal in this comparison. If multimodal input 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 4.20?
Gemini 3.1 Pro Preview Custom Tools is available on OpenRouter. Grok 4.20 is available on xAI Console and OpenRouter. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
Continue comparing
Last reviewed: 2026-05-20. Data sourced from public model cards and provider documentation.