Gemini 3.1 Pro Preview Custom Tools vs o3
Gemini 3.1 Pro Preview Custom Tools (2026) and o3 (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 ships a 200k-token context window. On pricing, both list $2/1M input tokens on the cheapest tracked route. This comparison covers specs, pricing, API access, capabilities, benchmarks, input and output token costs, and production fit for coding and agent workloads.
Gemini 3.1 Pro Preview Custom Tools fits 5x more tokens; pick it for long-context work and o3 for tighter calls.
Decision scorecard
Local evidence first| Signal | Gemini 3.1 Pro Preview Custom Tools | o3 |
|---|---|---|
| Best for | multimodal apps, long-context analysis, and provider-routed production | reasoning-heavy apps, multimodal apps, and tool-calling agents |
| Decision fit | RAG, Long context, and Vision | Coding, RAG, and Agents |
| Context window | 1m | 200k |
| Cheapest output | $12/1M tokens | $8/1M tokens |
| Provider routes | 2 tracked | 3 tracked |
| Shared benchmarks | 0 shared | 0 shared |
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 Vision.
- o3 has the lower cheapest tracked output price at $8/1M tokens.
- o3 has broader tracked provider coverage for fallback and route flexibility.
- o3 uniquely exposes Reasoning, JSON / Tool use, and Code execution in local model data.
- Local decision data tags o3 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
o3
$3,600
Cheapest tracked route/tier: OpenAI API
Estimated monthly gap: $1,000. 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.
- o3 is $4/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
- o3 adds Reasoning, JSON / Tool use, and Code execution in local capability data.
- Provider overlap exists on OpenRouter; start route-level A/B tests there.
- Gemini 3.1 Pro Preview Custom Tools is $4/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
- Check replacement coverage for Reasoning, JSON / Tool use, and Code execution before moving production traffic.
Specs
| Specification | ||
|---|---|---|
| Released | 2026-01-01 | 2025-04-16 |
| Context window | 1m | 200k |
| Parameters | — | — |
| Architecture | Decoder Only | Decoder Only |
| License | Proprietary | Proprietary |
| Openness | Proprietary | Proprietary |
| Weights | Not released | Not released |
| Code | Unknown | Unknown |
| Commercial use | Commercial use: conditional | Commercial use: conditional |
| Knowledge cutoff | 2025-01 | 2024-06 |
Pricing and availability
| Pricing attribute | Gemini 3.1 Pro Preview Custom Tools | o3 |
|---|---|---|
| Input price | $2/1M tokens | $2/1M tokens |
| Output price | $12/1M tokens | $8/1M tokens |
| Providers |
Capabilities
| Capability | Gemini 3.1 Pro Preview Custom Tools | o3 |
|---|---|---|
| Vision | Yes | Yes |
| Multimodal | Yes | Yes |
| Reasoning | No | Yes |
| JSON / Tool use | No | Yes |
| Structured outputs | Yes | Yes |
| Code execution | No | Yes |
| IDE integration | No | No |
| Computer use | No | No |
| Parallel agents | No | No |
Benchmarks
No shared benchmark scores are currently available for this pair.
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Last reviewed: 2026-06-29. Data sourced from public model cards and provider documentation.