chore: add openrouter example

Co-authored-by: Mochan <0xMochan@users.noreply.github.com>

rig-core/examples/openrouter_streaming_with_tools.rs

@@ -0,0 +1,118 @@
+use anyhow::Result;
+use rig::streaming::stream_to_stdout;
+use rig::{completion::ToolDefinition, providers, streaming::StreamingPrompt, tool::Tool};
+use serde::{Deserialize, Serialize};
+use serde_json::json;
+
+#[derive(Deserialize)]
+struct OperationArgs {
+    x: i32,
+    y: i32,
+}
+
+#[derive(Debug, thiserror::Error)]
+#[error("Math error")]
+struct MathError;
+
+#[derive(Deserialize, Serialize)]
+struct Adder;
+impl Tool for Adder {
+    const NAME: &'static str = "add";
+
+    type Error = MathError;
+    type Args = OperationArgs;
+    type Output = i32;
+
+    async fn definition(&self, _prompt: String) -> ToolDefinition {
+        ToolDefinition {
+            name: "add".to_string(),
+            description: "Add x and y together".to_string(),
+            parameters: json!({
+                "type": "object",
+                "properties": {
+                    "x": {
+                        "type": "number",
+                        "description": "The first number to add"
+                    },
+                    "y": {
+                        "type": "number",
+                        "description": "The second number to add"
+                    }
+                },
+                "required": ["x", "y"]
+            }),
+        }
+    }
+
+    async fn call(&self, args: Self::Args) -> Result<Self::Output, Self::Error> {
+        let result = args.x + args.y;
+        Ok(result)
+    }
+}
+
+#[derive(Deserialize, Serialize)]
+struct Subtract;
+impl Tool for Subtract {
+    const NAME: &'static str = "subtract";
+
+    type Error = MathError;
+    type Args = OperationArgs;
+    type Output = i32;
+
+    async fn definition(&self, _prompt: String) -> ToolDefinition {
+        serde_json::from_value(json!({
+            "name": "subtract",
+            "description": "Subtract y from x (i.e.: x - y)",
+            "parameters": {
+                "type": "object",
+                "properties": {
+                    "x": {
+                        "type": "number",
+                        "description": "The number to subtract from"
+                    },
+                    "y": {
+                        "type": "number",
+                        "description": "The number to subtract"
+                    }
+                },
+                "required": ["x", "y"]
+            }
+        }))
+        .expect("Tool Definition")
+    }
+
+    async fn call(&self, args: Self::Args) -> Result<Self::Output, Self::Error> {
+        let result = args.x - args.y;
+        Ok(result)
+    }
+}
+
+#[tokio::main]
+async fn main() -> Result<(), anyhow::Error> {
+    tracing_subscriber::fmt().init();
+    // Create agent with a single context prompt and two tools
+    let calculator_agent = providers::openrouter::Client::from_env()
+        .agent(providers::openrouter::GEMINI_FLASH_2_0)
+        .preamble(
+            "You are a calculator here to help the user perform arithmetic 
+            operations. Use the tools provided to answer the user's question. 
+            make your answer long, so we can test the streaming functionality, 
+            like 20 words",
+        )
+        .max_tokens(1024)
+        .tool(Adder)
+        .tool(Subtract)
+        .build();
+
+    println!("Calculate 2 - 5");
+    let mut stream = calculator_agent.stream_prompt("Calculate 2 - 5").await?;
+    stream_to_stdout(calculator_agent, &mut stream).await?;
+
+    if let Some(response) = stream.response {
+        println!("Usage: {:?}", response.usage)
+    };
+
+    println!("Message: {:?}", stream.choice);
+
+    Ok(())
+}