Google: Gemini 3.1 Pro Preview Custom Tools

google/gemini-3.1-pro-preview-customtools

Released Feb 25, 20261,048,576 context

Starting at $2/M input tokensStarting at $12/M output tokens$2/M audio tokens

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.

Providers for Gemini 3.1 Pro Preview Custom Tools

OpenRouter routes requests to the best providers that are able to handle your prompt size and parameters, with fallbacks to maximize uptime.

Performance for Gemini 3.1 Pro Preview Custom Tools

Compare different providers across OpenRouter

Effective Pricing for Gemini 3.1 Pro Preview Custom Tools

Actual cost per million tokens across providers over the past hour

Apps using Gemini 3.1 Pro Preview Custom Tools

Top public apps this month

Recent activity on Gemini 3.1 Pro Preview Custom Tools

Total usage per day on OpenRouter

Prompt

7.67M

Reasoning

940K

Completion

230K

Prompt tokens measure input size. Reasoning tokens show internal thinking before a response. Completion tokens reflect total output length.

Uptime stats for Gemini 3.1 Pro Preview Custom Tools

Uptime stats for Gemini 3.1 Pro Preview Custom Tools across all providers

Sample code and API for Gemini 3.1 Pro Preview Custom Tools

OpenRouter normalizes requests and responses across providers for you.

OpenRouter supports reasoning-enabled models that can show their step-by-step thinking process. Use the reasoning parameter in your request to enable reasoning, and access the reasoning_details array in the response to see the model's internal reasoning before the final answer. When continuing a conversation, preserve the complete reasoning_details when passing messages back to the model so it can continue reasoning from where it left off. Learn more about reasoning tokens.

In the examples below, the OpenRouter-specific headers are optional. Setting them allows your app to appear on the OpenRouter leaderboards.

Using third-party SDKs

For information about using third-party SDKs and frameworks with OpenRouter, please see our frameworks documentation.

See the Request docs for all possible fields, and Parameters for explanations of specific sampling parameters.