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Vertex

Gemini 3.1 Pro Preview Custom Tools API

Vertex
About

Build advanced reasoning agents with Gemini 3.1 Pro Preview Custom Tools, a specialized AI model optimized for complex logic and chain-of-thought tasks. This model delivers cost-effective pricing at $2.00/1M input and $12.00/1M output tokens, native tool calling support. Access Gemini 3.1 Pro Preview Custom Tools via the Vertex API with up to 66K output tokens.

Capabilities

Input Modalities

textimagevideoaudiopdf

Output Modalities

text
Reasoning
Yes
Structured Output
Yes
Tool Use
Yes
WeightsClosed
Temperature
Adjustable
Attachment
Supported
Limits
Context Window
1.0M

Tokens

Input Limit
1.0M

Tokens

Max Output
66K

Tokens

Pricing

Standard (per 1M tokens)

Input
$2.00
Output
$12.00

Caching (per 1M tokens)

Read
$0.20
Frequently Asked Questions

Gemini 3.1 Pro Preview Custom Tools by Vertex costs $2.00 per 1M input tokens and $12.00 per 1M output tokens. Cached reads cost $0.20 per 1M tokens.

Model Details
ID
gemini-3.1-pro-preview-customtools
Provider
Vertex
Family
gemini-pro
Release Date
Feb 19, 2026
Knowledge Cutoff
Jan 1, 2025
API Integration
NPM Package
@ai-sdk/google-vertex
Environment Variables
GOOGLE_VERTEX_PROJECT
GOOGLE_VERTEX_LOCATION
GOOGLE_APPLICATION_CREDENTIALS
Documentation