Key Takeaways
Gemini 3.1 Pro Preview Custom Tools wins:
- Larger context window
GPT-5 Codex wins:
- Cheaper input tokens
- Cheaper output tokens
- Faster response time
- Higher intelligence benchmark
- Better at coding
- Better at math
- Supports tool calls
Price Advantage
GPT-5 Codex
Benchmark Advantage
GPT-5 Codex
Context Window
Gemini 3.1 Pro Preview Custom Tools
Speed
GPT-5 Codex
Pricing Comparison
Price Comparison
| Metric | Gemini 3.1 Pro Preview Custom Tools | GPT-5 Codex | Winner |
|---|---|---|---|
| Input (per 1M tokens) | $2.00 | $1.25 | GPT-5 Codex |
| Output (per 1M tokens) | $12.00 | $10.00 | GPT-5 Codex |
| Cache Read (per 1M) | $0.20 | $0.13 | GPT-5 Codex |
| Cache Write (per 1M) | $0.38 | N/A | Gemini 3.1 Pro Preview Custom Tools |
Using a 3:1 input/output ratio, GPT-5 Codex is 24% cheaper overall.
Gemini 3.1 Pro Preview Custom Tools Providers
Google AI Studio $2.00 (Cheapest)
GPT-5 Codex Providers
OpenAI $1.25 (Cheapest)
Benchmark Comparison
6
Benchmarks Compared
0
Gemini 3.1 Pro Preview Custom Tools Wins
0
GPT-5 Codex Wins
Benchmark Scores
| Benchmark | Gemini 3.1 Pro Preview Custom Tools | GPT-5 Codex | Winner |
|---|---|---|---|
Intelligence Index Overall intelligence score | - | 44.6 | - |
Coding Index Code generation & understanding | - | 38.9 | - |
Math Index Mathematical reasoning | - | 98.7 | - |
MMLU Pro Academic knowledge | - | 86.5 | - |
GPQA Graduate-level science | - | 83.7 | - |
LiveCodeBench Competitive programming | - | 84.0 | - |
GPT-5 Codex significantly outperforms in coding benchmarks.
Cost vs Quality
X-axis:
Y-axis:
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Other models
Context & Performance
Context Window
Gemini 3.1 Pro Preview Custom Tools
1,048,576
tokens
Max output: 65,536 tokens
GPT-5 Codex
400,000
tokens
Max output: 128,000 tokens
Gemini 3.1 Pro Preview Custom Tools has a 62% larger context window.
Speed Performance
| Metric | Gemini 3.1 Pro Preview Custom Tools | GPT-5 Codex | Winner |
|---|---|---|---|
| Tokens/second | N/A | 308.6 tok/s | |
| Time to First Token | N/A | 12.67s |
Capabilities
Feature Comparison
| Feature | Gemini 3.1 Pro Preview Custom Tools | GPT-5 Codex |
|---|---|---|
| Vision (Image Input) | ||
| Tool/Function Calls | ||
| Reasoning Mode | ||
| Audio Input | ||
| Audio Output | ||
| PDF Input | ||
| Prompt Caching | ||
| Web Search |
License & Release
| Property | Gemini 3.1 Pro Preview Custom Tools | GPT-5 Codex |
|---|---|---|
| License | Proprietary | Proprietary |
| Author | OpenAI | |
| Released | Feb 2026 | Sep 2025 |
Gemini 3.1 Pro Preview Custom Tools Modalities
Input
textaudioimagevideofile
Output
text
GPT-5 Codex Modalities
Input
textimage
Output
text