Gemini 3.1 Pro Preview Custom Tools vs Gemini 3.5 Flash
A side-by-side comparison of two multimodal models — real specs, pricing, strengths and weaknesses, and a clear verdict on which to choose. Kept current by our agents.
Quick verdict: which should you choose?
Choose Gemini 3.1 Pro Preview Custom Tools if you need
- ✓custom tool extensions for flexible multimodal workflows
- ✓strong cross-modal coherence on mixed inputs
- ✓slightly larger 1,048,756-token context window
- ✓effective handling of very large context scenarios
Choose Gemini 3.5 Flash if you need
- ✓high output speed of 171.73 t/s for rapid responses
- ✓lower pricing at $9 per million tokens
- ✓strong multimodal integration across text, image, video and audio
- ✓efficient performance on high-volume tasks
Verdict
Gemini 3.5 Flash leads on speed and price with a documented 171.73 t/s output and $9/1M cost, while Gemini 3.1 Pro Preview Custom Tools provides custom-tool extensibility and a marginally larger 1,048,756-token context for mixed-input coherence. The Pro model’s preview status introduces potential instability risks absent from the Flash description. Overall, Flash suits efficiency-focused multimodal workloads; the Pro variant targets users needing tool customization despite higher cost.
Gemini 3.1 Pro Preview Custom Tools vs Gemini 3.5 Flash: side by side
| Spec | Gemini 3.1 Pro Preview Custom Tools | Gemini 3.5 Flash | Winner |
|---|---|---|---|
| Intelligence | — | 45.4 | Tie |
| Output speed | — | 172 t/s | Tie |
| Output price | $12.00/1M | $9.00/1M | Gemini 3.5 Flash |
| Context | 1049K | 1049K | Tie |
| Params | — | — | Tie |
| Provider | Tie |
Detailed analysis
Speed
Winner: Gemini 3.5 FlashGemini 3.5 Flash lists a concrete output speed of 171.73 t/s. Gemini 3.1 Pro Preview Custom Tools provides no speed metric. The Flash model’s design emphasizes high speed and efficiency while the Pro model notes potential latency increases with large contexts.
Pricing
Winner: Gemini 3.5 FlashGemini 3.5 Flash is priced at $9 per million tokens. Gemini 3.1 Pro Preview Custom Tools costs $12 per million tokens. The $3 difference favors Flash for cost-sensitive deployments.
Context Window
Winner: Gemini 3.1 Pro Preview Custom ToolsGemini 3.1 Pro Preview Custom Tools supports 1,048,756 tokens versus 1,048,576 for Gemini 3.5 Flash. Both models handle large contexts, yet the Pro variant’s strengths explicitly highlight effective use of very large windows.
Tool Integration
Winner: Gemini 3.1 Pro Preview Custom ToolsGemini 3.1 Pro Preview Custom Tools includes flexible extension via custom tools. Gemini 3.5 Flash lists no tool-related capabilities. This dimension gives the Pro model an edge for users requiring additional configuration options.
Gemini 3.1 Pro Preview Custom Tools
Pros
- +Strong cross-modal coherence on mixed inputs
- +Effective use of very large context windows
- +Flexible extension via custom tools
Cons
- –Preview status may include occasional instability
- –Large contexts can increase latency and cost
- –Tool setup requires additional configuration
Gemini 3.5 Flash
Pros
- +High speed and efficiency
- +Strong multimodal integration
- +Large context window support
Cons
- –Trades depth for speed on complex tasks
- –Variable performance on specialized domains
- –Context utilization depends on task
Summary: Gemini 3.1 Pro Preview Custom Tools vs Gemini 3.5 Flash
Choose Gemini 3.5 Flash when speed, lower cost, and efficient multimodal processing are priorities. Select Gemini 3.1 Pro Preview Custom Tools when custom tools and marginally larger context handling outweigh the higher price and preview-stage risks. The data show clear trade-offs between efficiency and extensibility.
Frequently asked questions
Gemini 3.5 Flash is faster, with a documented output speed of 171.73 t/s; no speed figure is provided for Gemini 3.1 Pro Preview Custom Tools.