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google/gemini-3-1-pro-preview-customtools
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Gemini 3.1 Pro Preview Custom Tools
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.
2/25/2026
1,048,576 tokens
Specifications
Modalities
Input
text
audio
image
video
file
Output
text
Supported Parameters
include_reasoning
max_tokens
reasoning
response_format
seed
stop
structured_outputs
temperature
tool_choice
tools
top_p
Max Output Tokens
65,536Reasoning Configuration
- Default
- Thinking on (effort: medium)
- Selectable effort levels
- highmediumlow
- Turning thinking off
- Not possible (always thinks)
Frequently asked questions
- Is Gemini 3.1 Pro Preview Custom Tools available on FastMetal?
- Not at the moment. GLM 5.3 Flash, from the same lab, is available on the FastMetal API today.
- What is the context window of Gemini 3.1 Pro Preview Custom Tools?
- 1,048,576 tokens, shared between the prompt and the response.