Gemini 3.1 Pro Preview Custom Tools vs o3-pro
Gemini 3.1 Pro Preview Custom Tools (2026) and o3-pro (2025) are frontier reasoning models from Google DeepMind and OpenAI. Gemini 3.1 Pro Preview Custom Tools ships a 1M-token context window, while o3-pro ships a not-yet-sourced context window. On pricing, Gemini 3.1 Pro Preview Custom Tools costs $2/1M input tokens versus $20/1M for the alternative. This comparison covers specs, pricing, capabilities, benchmarks, provider availability, and production fit.
Gemini 3.1 Pro Preview Custom Tools is ~900% cheaper at $2/1M; pay for o3-pro only for coding workflow support.
Specs
| Specification | ||
|---|---|---|
| Released | 2026-01-01 | 2025-06-10 |
| Context window | 1M | — |
| Parameters | — | — |
| Architecture | decoder only | decoder only |
| License | Unknown | Proprietary |
| Knowledge cutoff | - | 2025-08 |
Pricing and availability
| Pricing attribute | Gemini 3.1 Pro Preview Custom Tools | o3-pro |
|---|---|---|
| Input price | $2/1M tokens | $20/1M tokens |
| Output price | $12/1M tokens | $80/1M tokens |
| Providers |
Capabilities
| Capability | Gemini 3.1 Pro Preview Custom Tools | o3-pro |
|---|---|---|
| Vision | No | Yes |
| Multimodal | No | Yes |
| Reasoning | No | Yes |
| Function calling | No | Yes |
| Tool use | No | Yes |
| Structured outputs | Yes | Yes |
| Code execution | No | Yes |
Benchmarks
No shared benchmark rows are currently sourced for this pair.
Deep dive
The capability footprint differs most on vision: o3-pro, multimodal input: o3-pro, reasoning mode: o3-pro, function calling: o3-pro, tool use: o3-pro, and code execution: o3-pro. 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 o3-pro lists $20/1M input and $80/1M output tokens on the cheapest tracked provider. A 70/30 input-output blend puts Gemini 3.1 Pro Preview Custom Tools lower by about $33 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 and lower input-token cost are central to the workload. Choose o3-pro when coding workflow support 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 is cheaper, Gemini 3.1 Pro Preview Custom Tools or o3-pro?
Gemini 3.1 Pro Preview Custom Tools is cheaper on tracked token pricing. Gemini 3.1 Pro Preview Custom Tools costs $2/1M input and $12/1M output tokens. o3-pro costs $20/1M input and $80/1M output tokens. Provider discounts or batch pricing can still change the final bill.
Is Gemini 3.1 Pro Preview Custom Tools or o3-pro open source?
Gemini 3.1 Pro Preview Custom Tools is listed under Unknown. o3-pro 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 o3-pro?
o3-pro 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 o3-pro?
o3-pro 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.
Which is better for reasoning mode, Gemini 3.1 Pro Preview Custom Tools or o3-pro?
o3-pro 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.
Where can I run Gemini 3.1 Pro Preview Custom Tools and o3-pro?
Gemini 3.1 Pro Preview Custom Tools is available on OpenRouter. o3-pro is available on OpenRouter and OpenAI API. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
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Last reviewed: 2026-05-11. Data sourced from public model cards and provider documentation.