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Gemini 3.1 Pro Preview Custom Tools

GoogleReleased Feb 25, 2026

Gemini 3.1 Pro Preview Custom Tools is a variant of Gemini 3.1 Pro that improves tool selection behavior by preventing overuse of a general bash tool when more efficient third-party...

Try in playground
Context window
1.0M tokens
Max output
66K tokens
Input
text, audio, image, video, file
Output
text
Tokenizer
Gemini
Released
Feb 25, 2026
Reasoning
always on

Pricing

Per 1M tokens. The provider price and our flat 3% fee are separate columns — what you pay is their sum.

Per 1M tokensProvider+ 3% feeYou pay
Input$2.00$0.060$2.06
Output$12.00$0.360$12.36
Cache read$0.200$0.0060$0.206
Cache write$0.375$0.011$0.386

Supported parameters

  • include_reasoning
  • max_tokens
  • reasoning
  • response_format
  • seed
  • structured_outputs
  • temperature
  • tool_choice
  • tools
  • top_p

Call it

OpenAI-compatible: point your SDK at api.openkey.ai/v1 and use model google/gemini-3.1-pro-preview-customtools.

Code sample language
curl https://api.openkey.ai/v1/chat/completions \
  -H "Authorization: Bearer $OPENKEY_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "google/gemini-3.1-pro-preview-customtools",
    "messages": [{"role": "user", "content": "Hello"}]
  }'
import os
from openai import OpenAI

client = OpenAI(
    base_url="https://api.openkey.ai/v1",
    api_key=os.environ["OPENKEY_API_KEY"],
)

completion = client.chat.completions.create(
    model="google/gemini-3.1-pro-preview-customtools",
    messages=[{"role": "user", "content": "Hello"}],
)
print(completion.choices[0].message.content)
import OpenAI from "openai";

const client = new OpenAI({
  baseURL: "https://api.openkey.ai/v1",
  apiKey: process.env.OPENKEY_API_KEY,
});

const completion = await client.chat.completions.create({
  model: "google/gemini-3.1-pro-preview-customtools",
  messages: [{ role: "user", content: "Hello" }],
});
console.log(completion.choices[0].message.content);

Questions

How much does Gemini 3.1 Pro Preview Custom Tools cost via API?
Through OpenKey, Gemini 3.1 Pro Preview Custom Tools costs $2.06 per 1M input tokens and $12.36 per 1M output tokens. That is the provider price ($2.00 / $12.00) plus a flat 3% fee — nothing else.
What is Gemini 3.1 Pro Preview Custom Tools's context window?
Gemini 3.1 Pro Preview Custom Tools accepts up to 1.0M tokens of context and returns up to 66K tokens per request.
Is Gemini 3.1 Pro Preview Custom Tools OpenAI-compatible?
Yes. Send requests to OpenKey's /v1/chat/completions endpoint with model "google/gemini-3.1-pro-preview-customtools" using any OpenAI SDK — only the base URL and API key change.
What inputs does Gemini 3.1 Pro Preview Custom Tools support?
Gemini 3.1 Pro Preview Custom Tools accepts text, audio, image, video, file input and produces text output.

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