Tools let your agent call custom functions — like fetching weather data, querying a database, or calling an API.

:::zone pivot="programming-language-csharp"

Define a tool as any method with a [Description] attribute:

using System.ComponentModel;

[Description("Get the weather for a given location.")]
static string GetWeather([Description("The location to get the weather for.")] string location)
    => $"The weather in {location} is cloudy with a high of 15°C.";

Create an agent with the tool:

using System;
using Azure.AI.Projects;
using Azure.Identity;
using Microsoft.Agents.AI;
using Microsoft.Extensions.AI;

var endpoint = Environment.GetEnvironmentVariable("AZURE_OPENAI_ENDPOINT")
    ?? throw new InvalidOperationException("Set AZURE_OPENAI_ENDPOINT");
var deploymentName = Environment.GetEnvironmentVariable("AZURE_OPENAI_DEPLOYMENT_NAME") ?? "gpt-4o-mini";

AIAgent agent = new AIProjectClient(new Uri(endpoint), new DefaultAzureCredential())
    .AsAIAgent(
        model: deploymentName,
        instructions: "You are a helpful assistant.",
        tools: [AIFunctionFactory.Create(GetWeather)]);

The agent will automatically call your tool when relevant:

Console.WriteLine(await agent.RunAsync("What is the weather like in Amsterdam?"));

:::zone-end

:::zone pivot="programming-language-python"

Define a tool with the @tool decorator:

:::code language="python" source="~/../agent-framework-code/python/samples/01-get-started/02_add_tools.py" id="define_tool" highlight="3":::

Create an agent with the tool:

:::code language="python" source="~/../agent-framework-code/python/samples/01-get-started/02_add_tools.py" id="create_agent_with_tools" highlight="4":::

:::zone-end

:::zone pivot="programming-language-go"

Define a tool using functool:

import (
    "context"
    "fmt"

    "github.com/microsoft/agent-framework-go/tool"
    "github.com/microsoft/agent-framework-go/tool/functool"
)

var weatherTool = functool.MustNew(functool.Config{
    Name:        "weather",
    Description: "Get the current weather for a given location",
}, func(_ context.Context, location string) (string, error) {
    return fmt.Sprintf("The weather in %s is cloudy with a high of 15°C.", location), nil
})

Create an agent with the tool:

a := foundryprovider.NewAgent(
    endpoint,
    token,
    foundryprovider.ModelDeployment(model),
    foundryprovider.AgentConfig{
        Instructions: "You are a helpful assistant",
        Config: agent.Config{
            Tools: []tool.Tool{weatherTool},
        },
    },
)

The agent will automatically call your tool when relevant:

resp, err := a.RunText(ctx, "What is the weather like in Amsterdam?").Collect()
fmt.Println(resp, err)

:::zone-end

[!div class="nextstepaction"] Step 3: Multi-Turn Conversations

Go deeper:

• Tools overview — learn about all available tool types
• Function tools — advanced function tool patterns
• Tool approval — human-in-the-loop for tool calls