Example: Giving an Agent a Tool

import { Mastra } from "@mastra/core";
import { Agent } from "@mastra/core/agent";
import { createTool } from "@mastra/core/tools";
import { openai } from "@ai-sdk/openai";
import { z } from "zod";
 
interface WeatherResponse {
  current: {
    time: string;
    temperature_2m: number;
    apparent_temperature: number;
    relative_humidity_2m: number;
    wind_speed_10m: number;
    wind_gusts_10m: number;
    weather_code: number;
  };
}
 
const weatherTool = createTool({
  id: "get-weather",
  description: "Get current weather for a location",
  inputSchema: z.object({
    location: z.string().describe("City name"),
  }),
  outputSchema: z.object({
    temperature: z.number(),
    feelsLike: z.number(),
    humidity: z.number(),
    windSpeed: z.number(),
    windGust: z.number(),
    conditions: z.string(),
    location: z.string(),
  }),
  execute: async ({ context }) => {
    return await getWeather(context.location);
  },
});
 
const getWeather = async (location: string) => {
  const geocodingUrl = `https://geocoding-api.open-meteo.com/v1/search?name=${encodeURIComponent(location)}&count=1`;
  const geocodingResponse = await fetch(geocodingUrl);
  const geocodingData = await geocodingResponse.json();
 
  if (!geocodingData.results?.[0]) {
    throw new Error(`Location '${location}' not found`);
  }
 
  const { latitude, longitude, name } = geocodingData.results[0];
 
  const weatherUrl = `https://api.open-meteo.com/v1/forecast?latitude=${latitude}&longitude=${longitude}&current=temperature_2m,apparent_temperature,relative_humidity_2m,wind_speed_10m,wind_gusts_10m,weather_code`;
 
  const response = await fetch(weatherUrl);
  const data: WeatherResponse = await response.json();
 
  return {
    temperature: data.current.temperature_2m,
    feelsLike: data.current.apparent_temperature,
    humidity: data.current.relative_humidity_2m,
    windSpeed: data.current.wind_speed_10m,
    windGust: data.current.wind_gusts_10m,
    conditions: getWeatherCondition(data.current.weather_code),
    location: name,
  };
};
 
function getWeatherCondition(code: number): string {
  const conditions: Record<number, string> = {
    0: "Clear sky",
    1: "Mainly clear",
    2: "Partly cloudy",
    3: "Overcast",
    45: "Foggy",
    48: "Depositing rime fog",
    51: "Light drizzle",
    53: "Moderate drizzle",
    55: "Dense drizzle",
    56: "Light freezing drizzle",
    57: "Dense freezing drizzle",
    61: "Slight rain",
    63: "Moderate rain",
    65: "Heavy rain",
    66: "Light freezing rain",
    67: "Heavy freezing rain",
    71: "Slight snow fall",
    73: "Moderate snow fall",
    75: "Heavy snow fall",
    77: "Snow grains",
    80: "Slight rain showers",
    81: "Moderate rain showers",
    82: "Violent rain showers",
    85: "Slight snow showers",
    86: "Heavy snow showers",
    95: "Thunderstorm",
    96: "Thunderstorm with slight hail",
    99: "Thunderstorm with heavy hail",
  };
  return conditions[code] || "Unknown";
}
 
const weatherAgent = new Agent({
  name: "Weather Agent",
  instructions: `You are a helpful weather assistant that provides accurate weather information.
Your primary function is to help users get weather details for specific locations. When responding:
- Always ask for a location if none is provided
- If the location name isn’t in English, please translate it
- Include relevant details like humidity, wind conditions, and precipitation
- Keep responses concise but informative
Use the weatherTool to fetch current weather data.`,
  model: openai("gpt-4o-mini"),
  tools: { weatherTool },
});
 
const mastra = new Mastra({
  agents: { weatherAgent },
});
 
async function main() {
  const agent = await mastra.getAgent("weatherAgent");
  const result = await agent.generate("What is the weather in London?");
  console.log(result.text);
}
 
main();