You’ll need a weather API key. This example uses WeatherAPI (free tier available).
The tool includes proper error handling:
$ pnpm add @openrouter/sdk zod
$ export WEATHER_API_KEY=your_api_key_here > export OPENROUTER_API_KEY=your_openrouter_key
1 import { OpenRouter, tool } from '@openrouter/sdk'; 2 import { z } from 'zod'; 3 4 const openrouter = new OpenRouter({ 5 apiKey: process.env.OPENROUTER_API_KEY, 6 }); 7 8 const weatherTool = tool({ 9 name: 'get_weather', 10 description: 'Get current weather conditions for any city worldwide', 11 inputSchema: z.object({ 12 city: z.string().describe('City name, e.g., "San Francisco" or "London, UK"'), 13 units: z 14 .enum(['celsius', 'fahrenheit']) 15 .default('celsius') 16 .describe('Temperature units'), 17 }), 18 outputSchema: z.object({ 19 temperature: z.number(), 20 feelsLike: z.number(), 21 conditions: z.string(), 22 humidity: z.number(), 23 windSpeed: z.number(), 24 windDirection: z.string(), 25 location: z.object({ 26 name: z.string(), 27 region: z.string(), 28 country: z.string(), 29 }), 30 }), 31 execute: async ({ city, units }) => { 32 const apiKey = process.env.WEATHER_API_KEY; 33 if (!apiKey) { 34 throw new Error('WEATHER_API_KEY environment variable not set'); 35 } 36 37 const response = await fetch( 38 `https://api.weatherapi.com/v1/current.json?key=${apiKey}&q=${encodeURIComponent(city)}` 39 ); 40 41 if (!response.ok) { 42 if (response.status === 400) { 43 throw new Error(`City not found: ${city}`); 44 } 45 throw new Error(`Weather API error: ${response.status}`); 46 } 47 48 const data = await response.json(); 49 50 return { 51 temperature: units === 'celsius' ? data.current.temp_c : data.current.temp_f, 52 feelsLike: units === 'celsius' ? data.current.feelslike_c : data.current.feelslike_f, 53 conditions: data.current.condition.text, 54 humidity: data.current.humidity, 55 windSpeed: data.current.wind_kph, 56 windDirection: data.current.wind_dir, 57 location: { 58 name: data.location.name, 59 region: data.location.region, 60 country: data.location.country, 61 }, 62 }; 63 }, 64 });
1 const result = openrouter.callModel({ 2 model: 'openai/gpt-5-nano', 3 input: 'What is the weather like in Tokyo?', 4 tools: [weatherTool], 5 }); 6 7 const text = await result.getText(); 8 console.log(text); 9 // "The current weather in Tokyo, Japan is partly cloudy with a temperature 10 // of 22°C (feels like 24°C). Humidity is at 65% with winds from the SW 11 // at 15 km/h."
1 const result = openrouter.callModel({ 2 model: 'openai/gpt-5-nano', 3 input: 'Compare the weather in New York and Los Angeles', 4 tools: [weatherTool], 5 }); 6 7 // The model will call the tool twice, once for each city 8 const text = await result.getText();
1 const forecastTool = tool({ 2 name: 'get_forecast', 3 description: 'Get weather forecast for the next few days', 4 inputSchema: z.object({ 5 city: z.string().describe('City name'), 6 days: z.number().min(1).max(7).default(3).describe('Number of forecast days'), 7 units: z.enum(['celsius', 'fahrenheit']).default('celsius'), 8 }), 9 outputSchema: z.object({ 10 location: z.string(), 11 forecast: z.array( 12 z.object({ 13 date: z.string(), 14 maxTemp: z.number(), 15 minTemp: z.number(), 16 conditions: z.string(), 17 chanceOfRain: z.number(), 18 }) 19 ), 20 }), 21 execute: async ({ city, days, units }) => { 22 const apiKey = process.env.WEATHER_API_KEY; 23 if (!apiKey) { 24 throw new Error('WEATHER_API_KEY environment variable not set'); 25 } 26 27 const response = await fetch( 28 `https://api.weatherapi.com/v1/forecast.json?key=${apiKey}&q=${encodeURIComponent(city)}&days=${days}` 29 ); 30 31 if (!response.ok) { 32 throw new Error(`Weather API error: ${response.status}`); 33 } 34 35 const data = await response.json(); 36 37 return { 38 location: `${data.location.name}, ${data.location.country}`, 39 forecast: data.forecast.forecastday.map((day: any) => ({ 40 date: day.date, 41 maxTemp: units === 'celsius' ? day.day.maxtemp_c : day.day.maxtemp_f, 42 minTemp: units === 'celsius' ? day.day.mintemp_c : day.day.mintemp_f, 43 conditions: day.day.condition.text, 44 chanceOfRain: day.day.daily_chance_of_rain, 45 })), 46 }; 47 }, 48 }); 49 50 // Use both tools together 51 const result = openrouter.callModel({ 52 model: 'openai/gpt-5-nano', 53 input: 'What is the weather in Paris today and for the next 3 days?', 54 tools: [weatherTool, forecastTool], 55 });
1 const weatherToolWithRetry = tool({ 2 name: 'get_weather', 3 description: 'Get current weather with retry logic', 4 inputSchema: z.object({ 5 city: z.string(), 6 units: z.enum(['celsius', 'fahrenheit']).default('celsius'), 7 }), 8 outputSchema: z.object({ 9 temperature: z.number(), 10 conditions: z.string(), 11 error: z.string().optional(), 12 }), 13 execute: async ({ city, units }) => { 14 const maxRetries = 3; 15 let lastError: Error | null = null; 16 17 for (let attempt = 1; attempt <= maxRetries; attempt++) { 18 try { 19 const response = await fetch( 20 `https://api.weatherapi.com/v1/current.json?key=${process.env.WEATHER_API_KEY}&q=${encodeURIComponent(city)}` 21 ); 22 23 if (response.status === 429) { 24 // Rate limited, wait and retry 25 await new Promise((resolve) => setTimeout(resolve, 1000 * attempt)); 26 continue; 27 } 28 29 if (!response.ok) { 30 throw new Error(`API error: ${response.status}`); 31 } 32 33 const data = await response.json(); 34 return { 35 temperature: units === 'celsius' ? data.current.temp_c : data.current.temp_f, 36 conditions: data.current.condition.text, 37 }; 38 } catch (error) { 39 lastError = error as Error; 40 } 41 } 42 43 // Return error in output rather than throwing 44 return { 45 temperature: 0, 46 conditions: 'Unknown', 47 error: `Failed after ${maxRetries} attempts: ${lastError?.message}`, 48 }; 49 }, 50 });
1 import { describe, it, expect, mock } from 'bun:test'; 2 3 describe('weatherTool', () => { 4 it('returns weather data for valid city', async () => { 5 // Mock the fetch response 6 global.fetch = mock(() => 7 Promise.resolve({ 8 ok: true, 9 json: () => 10 Promise.resolve({ 11 current: { 12 temp_c: 22, 13 temp_f: 72, 14 feelslike_c: 24, 15 feelslike_f: 75, 16 condition: { text: 'Sunny' }, 17 humidity: 45, 18 wind_kph: 10, 19 wind_dir: 'NW', 20 }, 21 location: { 22 name: 'London', 23 region: 'City of London', 24 country: 'UK', 25 }, 26 }), 27 }) 28 ); 29 30 const result = await weatherTool.function.execute( 31 { city: 'London', units: 'celsius' }, 32 { numberOfTurns: 1 } 33 ); 34 35 expect(result.temperature).toBe(22); 36 expect(result.conditions).toBe('Sunny'); 37 expect(result.location.name).toBe('London'); 38 }); 39 40 it('handles city not found', async () => { 41 global.fetch = mock(() => 42 Promise.resolve({ 43 ok: false, 44 status: 400, 45 }) 46 ); 47 48 await expect( 49 weatherTool.function.execute( 50 { city: 'InvalidCity123', units: 'celsius' }, 51 { numberOfTurns: 1 } 52 ) 53 ).rejects.toThrow('City not found'); 54 }); 55 });