Gemini 3.1 Pro Preview Custom Tools

Gemini 3.1 Pro Preview Custom Tools is presented as a routing variant of Google's Gemini 3.1 Pro Preview, where the underlying model is reached through custom tools and provider-specific integrations rather than the default serving path. This positioning makes the variant most relevant to developers who want to experiment with bespoke tool-calling pipelines, structured workflows, or function-calling harnesses layered on top of a frontier-tier Google model. The attribution to Google is consistent across available third-party listings, reinforcing that the core language and multimodal capabilities originate with Google's Gemini family rather than being a separate model family entirely.

In practical terms, the variant is aimed at long-context and reasoning-heavy workloads. Aggregator listings describe it as well-suited to deep reasoning, vision and multimodal input, analysis, function calling, tool use, and code generation, all supported by an exceptionally large input window suitable for whole-codebase or whole-document analysis. Because it sits at the "deep" speed tier, the model is framed for thorough, carefully considered answers rather than quick replies, fitting complex agentic and analytical tasks where tool orchestration and richer reasoning outweigh low-latency concerns.