Google · language model
Gemini 3.1 Pro Preview Custom Tools: pricing, context and benchmarks
Gemini 3.1 Pro Preview Custom Tools is Google's model released on February 25, 2026. It costs $2 per million input tokens and $12 per million output tokens, with a 1M-token context window. No independent score has been published for it so far.
| Price | 4/30 | |
|---|---|---|
| Context | 14/15 | |
| Features | 11/15 |
What you need to know about Gemini 3.1 Pro Preview Custom Tools
Google, based in United States, put Gemini 3.1 Pro Preview Custom Tools online on February 25, 2026. It accepts text, audio, images, video, and files as input and produces text. Its context window reaches 1,048,576 tokens, larger than 93 % of the models in the registry, and it can write up to 65,536 tokens in one go.
It has been available for about 8 months, long enough for its prices and scores to have settled.
Gemini 3.1 Pro Preview Custom Tools pricing
On OpenRouter, Gemini 3.1 Pro Preview Custom Tools costs $2 per million input tokens and $12 per million output tokens. Counting three tokens read for every token written, its average price is $4.5 per million, more expensive than 88 % of paid models (5.9 times the median of $0.76).
A concrete example: a task that sends 2,000 tokens (about 1,500 words) and receives a 500-token answer costs $0.01. At 1,000 tasks a day, budget $300 a month. The price calculator redoes this with your own volumes.
Tokens already sent and cached are billed at $0.2 per million.
Performance and benchmarks
Epoch AI does not yet publish a capabilities index for Gemini 3.1 Pro Preview Custom Tools. We therefore show no made-up performance rating: only price, context and features count towards its score.
Scores published by Epoch AI on the benchmarks the site tracks:
| Benchmark | What it measures | Score | Date |
|---|---|---|---|
| SWE-bench Verified | fixing real GitHub issues | 75.6 % | Feb 19, 2026 |
Features, privacy and local use
- It supports tool calling, so it can drive an AI agent, call APIs or MCP servers.
- It can answer in an enforced JSON format (structured outputs).
- It is a reasoning model: it "thinks" before answering, which helps on hard tasks but uses more output tokens.
Its weights are not published: it can only be used through the Google API or a broker such as OpenRouter, which means sending your data off your machines.
Other Google models
| Model | Released | Avg. price | ECI |
|---|---|---|---|
| Gemini 4 Argon | Oct 13, 2026 | $4 | 166.5 |
| Nano Banana 2.1 | Oct 6, 2026 | $3 | — |
| Gemini 3.8 Flash | Sep 2, 2026 | $1.65 | 157.4 |
| Gemini 3.7 Flash | Aug 13, 2026 | $1.5 | 158 |
| Gemini 3.6 Flash | Jul 21, 2026 | $1.5 | 154.5 |
| Gemini 3.5 Flash Lite | Jul 21, 2026 | $0.85 | 144.9 |
| Nano Banana 2 Lite (Gemini 3.1 Flash Lite Image) | Jun 30, 2026 | $0.56 | — |
| Nano Banana 2 (Gemini 3.1 Flash Image) | Jun 18, 2026 | $1.13 | — |
Verdict
Computed score: 48/100, from public data (performance, price, context, features).
Strengths
- Very large context (1M tokens): long documents or a whole codebase fit in one request.
- Agent-ready: tool calling and structured JSON output.
Limitations
- Expensive: costlier than 88 % of paid models.
- No independent score published: performance cannot be verified.
Avoid if…
- you process large volumes on a tight budget;
- your data must not leave your servers;
- your tasks are mostly simple: a non-reasoning model will cost less.
Alternatives
Comparisons and tools
Learn more
Frequently asked questions
How much does Gemini 3.1 Pro Preview Custom Tools cost?
$2 per million input tokens and $12 per million output tokens on OpenRouter (checked October 25, 2026). A task with 2,000 tokens read and 500 written costs $0.01.
How big is Gemini 3.1 Pro Preview Custom Tools's context window?
1,048,576 tokens, roughly 786,000 words, with a maximum of 65,536 output tokens.
Can Gemini 3.1 Pro Preview Custom Tools run locally?
No, Google does not publish its weights: it is API-only.
Is Gemini 3.1 Pro Preview Custom Tools suitable for an AI agent?
Technically yes: it supports tool calling and structured outputs. Then check its cost for your volume.
What are the alternatives to Gemini 3.1 Pro Preview Custom Tools?
The closest models on price and performance are MiMo-V2.6-Pro-UltraSpeed, GPT-5.6 Terra, and Ember-1.
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Neutrality. No affiliate links. No vendor pays to be reviewed, rated or ranked. Reviews are directed by François Chollet, neutral and factual, and every data point is dated and sourced. How we score