Native tools

Some tools are built into the provider itself: Gemini can run code or query Google Search, OpenAI can search the web or generate images. You do not write or host these. You turn them on, and the model uses them as part of its turn.

Native tools are configured on the provider builder, while your own #[tool] functions are registered on the chat builder with .with_tools(...). Whether the two can be used together in the same request depends on the provider, and Gemini is finicky here. See combining native and custom tools before you mix them.

Gemini

Call the with_* methods on GeminiBuilder before build:

use chat_rs::gemini::GeminiBuilder;

let client = GeminiBuilder::new()
    .with_model("gemini-2.5-flash")
    .with_code_execution()
    .build();

with_google_maps takes an optional (lat, lng) to anchor results and a bool for whether to enable the maps widget. You can stack native tools together:

let client = GeminiBuilder::new()
    .with_model("gemini-2.5-flash")
    .with_google_maps(Some((34.05048, -118.24853)), false)
    .with_google_search()
    .build();

OpenAI

OpenAI exposes its native tools the same way, on OpenAIBuilder. Both with_web_search and with_image_generation take their respective config:

use chat_rs::openai::OpenAIBuilder;

let client = OpenAIBuilder::new()
    .with_model("gpt-4o")
    .with_web_search(None, None)
    .build();

with_web_search accepts an optional context size and an optional user location; passing None for both uses the provider defaults. with_image_generation takes an ImageGenerationTool describing the image output you want.

Combining native and custom tools

Stacking several native tools on one provider is fine (the Gemini Maps plus Search example above does exactly that). Combining native tools with your own #[tool] functions is the part that varies by provider.

When you need both with Gemini, you have two options: split the work across turns (one request uses the native tool, the next uses your custom tools), or route tool-calling requests to a provider that does support custom tools, while sending the rest to Gemini. The router is built for exactly this kind of capability-based routing; its capability example excludes Gemini whenever custom tools are in play.