Google: Gemini 3.1 Pro Preview Custom Tools

GoogleID: google/gemini-3.1-pro-preview-customtools

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 or user-defined functions are available. This specialized preview endpoint significantly increases function calling reliability and ensures the model selects the most appropriate tool in coding agents and complex, multi-tool workflows. It retains the core strengths of Gemini 3.1 Pro, including multimodal reasoning across text, image, video, audio, and code, a 1M-token context window, and strong software engineering performance.

Pricing per 1M Tokens

Input (Prompt)$2.00
Output (Completion)$12
Cache Read$0.20
Cache Write$0.38
Image$2.00

Specifications

Context Length1.0M
Max Output Tokens66K
Input ModalitiesText + Audio + Image + Video + File
Output ModalitiesText
TokenizerGemini
Instruct TypeN/A
Top Provider Context1.0M
Top Provider Max Output66K
ModeratedNo

Compare this model

See how Google: Gemini 3.1 Pro Preview Custom Tools stacks up against other models.

vs Google: Gemini 3.1 Flash Lite Previewvs Google: Nano Banana 2 (Gemini 3.1 Flash Image Preview)vs Google: Gemini 3.1 Pro Previewvs Google: Gemini 3 Flash Previewvs Google: Nano Banana Pro (Gemini 3 Pro Image Preview)

More from Google

Google: Gemini 3.1 Flash Lite Preview
Input$0.25
Context1.0M
Google: Nano Banana 2 (Gemini 3.1 Flash Image Preview)
Input$0.50
Context66K
Google: Gemini 3.1 Pro Preview
Input$2.00
Context1.0M
Google: Gemini 3 Flash Preview
Input$0.50
Context1.0M
Google: Nano Banana Pro (Gemini 3 Pro Image Preview)
Input$2.00
Context66K

Last updated: March 23, 2026

First tracked: March 23, 2026