function_calling/
function_calling.rs

1use gemini_client_api::gemini::ask::Gemini;
2use gemini_client_api::gemini::types::request::Tool;
3use gemini_client_api::gemini::types::sessions::Session;
4use gemini_client_api::gemini::utils::{execute_function_calls, gemini_function, GeminiSchema};
5use std::env;
6use std::error::Error;
7
8/// This function will be made available to Gemini.
9/// The doc comments are used as descriptions for the tool.
10#[gemini_function]
11/// Returns the result of adding two numbers.
12fn add_numbers(
13    /// The first number.
14    a: f64,
15    /// The second number.
16    b: f64,
17) -> f64 {
18    println!("[Executing Tool] adding {} + {}", a, b);
19    a + b
20}
21
22#[gemini_function]
23/// Mock function to get the current temperature.
24fn get_temperature(location: String) -> String {
25    println!("[Executing Tool] getting temperature for {}", location);
26    format!("25°C in {}", location)
27}
28
29#[tokio::main]
30async fn main() -> Result<(), Box<dyn Error>> {
31    let mut session = Session::new(10);
32    let api_key = env::var("GEMINI_API_KEY").expect("GEMINI_API_KEY must be set");
33    
34    // 1. Initialize Gemini and register tools
35    let ai = Gemini::new(api_key, "gemini-2.5-flash", None)
36        .set_tools(vec![Tool::FunctionDeclarations(vec![
37            add_numbers::gemini_schema(),
38            get_temperature::gemini_schema(),
39        ])]);
40
41    println!("--- Function Calling Example ---");
42    let prompt = "What is 123.45 plus 678.9, and what's the weather like in London?";
43    println!("User: {}\n", prompt);
44
45    // 2. Ask Gemini. It might reply with one or more function calls.
46    let mut response = ai.ask(session.ask_string(prompt)).await?;
47
48    // 3. Loop to handle potential multiple rounds of function calls
49    loop {
50        if response.get_chat().has_function_call() {
51            println!("Gemini requested function calls...");
52            
53            // 4. Use the macro to execute all requested calls and update the session
54            let results = execute_function_calls!(session, add_numbers, get_temperature);
55            
56            for (idx, res) in results.iter().enumerate() {
57                if let Some(r) = res {
58                    println!("  Call #{} result: {:?}", idx, r);
59                }
60            }
61
62            // 5. Send the results back to Gemini to get the final natural language response
63            response = ai.ask(&mut session).await?;
64        } else {
65            // No more function calls, show the final response
66            println!("\nGemini: {}", response.get_chat().get_text_no_think(""));
67            break;
68        }
69    }
70
71    Ok(())
72}
function_calling/function_calling.rs

function_calling/
function_calling.rs
