Gemini 3.1 Pro Preview Custom Tools

Gemini 3.1 Pro Preview Custom Tools is a specialized variant of the standard Gemini 3.1 Pro, engineered specifically to address challenges in tool selection and function calling. The model's design philosophy centers on preventing the overuse of a general-purpose bash tool when more efficient, third-party, or user-defined functions are available. This targeted refinement makes it particularly valuable for coding agents and complex workflows that require reliable tool orchestration. It retains the core multimodal reasoning capabilities of its parent model, processing text, images, video, audio, and code, alongside structured output generation and reasoning mode.

This specialized preview endpoint significantly increases function calling reliability and ensures the model selects the most appropriate tool for each task in multi-tool scenarios. The design draws on Google's broader Gemini 3.1 Pro architecture while introducing targeted improvements for scenarios where precise tool selection matters. The variant maintains strong software engineering performance and content moderation features, positioning it as a practical choice for development environments and automated systems that depend on coordinated tool use. Its focus on efficient tool routing makes it especially suited for applications requiring the model to intelligently choose between multiple available functions rather than defaulting to generic solutions.