Model details
Gemini 3.1 Pro Preview Custom Tools is a targeted variant of Google's Gemini 3.1 Pro family designed to refine how the model chooses between available functions during agentic runs. Rather than falling back on a general bash tool, the model is tuned to prefer more efficient third-party or user-defined functions when they are available, addressing a common friction point in multi-step tool orchestration where developers observe unnecessary shell-execution overhead. This behavioral focus positions the preview as a specialized drop rather than a general-purpose upgrade, making it especially relevant for pipelines that chain many function calls together and need lean, deterministic tool routing.
In practice, the variant inherits Gemini 3.1 Pro's broad multimodal input handling across text, audio, image, video, and PDF files, while producing text-only responses suitable for downstream parsing. It is well-suited to image-grounded analysis, long-document workflows, and structured-output tasks where reasoning and tool calling reinforce each other. Teams building agent stacks, retrieval-augmented assistants, or automated research pipelines can lean on this preview when they want a Pro-class model that picks the right specialized function instead of defaulting to a generic shell, with the understanding that it remains a preview iteration subject to further refinement.
Transparent token rates
Rates are shown per one million tokens. Combined means one million input plus one million output tokens.
OpenRouter
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. $2 per million input tokens, $12 per million output tokens. 1,048,756 token context window, maxim
OpenRouter
Complete guide to Google: Gemini 3.1 Pro Preview Custom Tools via OpenRouter: pricing, capabilities, setup with TypingMind, and real-world use cases.
OpenRouter
OpenRouter's comparison page pairs Gemini 3.1 Pro Preview against the Gemini 3.1 Pro Preview Custom Tools variant, showing that both originate from Google AI Studio and share a 1.05M-token context window along with identical list pricing of $2/M input, $12/M output, $0.20/M cached input, $0.375/M cache write, and $2/M The same comparison highlights that Gemini 3.1 Pro Preview is offered through 2 providers on OpenRouter while the Custom Tools variant is currently available through a single provider. Web search add-on pricing is listed at $14 per 1K calls for the base Preview but is shown as not offered for the Custom Tools build, wh
OpenRouter
Pi.dev documents Google's Gemini 3.1 Pro Preview Custom Tools as exposed through OpenRouter under the openai-completions API endpoint at https://openrouter.ai/api/v1, with the model id google/gemini-3.1-pro-preview-customtools. The listing shows a 1,048,576-token context window, a 65,536 maximum output, text and image The Pi page also surfaces OpenRouter-specific compatibility metadata for the variant, including supportsStore, supportsReasoningEffort, supportsUsageInStreaming, supportsStrictMode, and supportsLongCacheRetention, while noting that supportsDeveloperRole is unavailable and that the API uses an openrouter thinkingFormat
OpenRouter
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. $2 per million input tokens, $12 per million output tokens. 1,048,576 token context window, maxim
This exact model name is also listed by 10 other providers.
