middleware

Adding Middleware to Agents

Learn how to add middleware to your agents in a few simple steps. Middleware allows you to intercept and modify agent interactions for logging, security, and other cross-cutting concerns.

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

Prerequisites

For prerequisites and installing NuGet packages, see the Create and run a simple agent step in this tutorial.

Step 1: Create a Simple Agent

First, create a basic agent with a function tool.

using System;
using System.ComponentModel;
using Azure.AI.OpenAI;
using Azure.Identity;
using Microsoft.Agents.AI;
using Microsoft.Extensions.AI;
using OpenAI;

[Description("The current datetime offset.")]
static string GetDateTime()
    => DateTimeOffset.Now.ToString();

AIAgent baseAgent = new AzureOpenAIClient(
    new Uri("https://<myresource>.openai.azure.com"),
    new AzureCliCredential())
        .GetChatClient("gpt-4o-mini")
        .AsAIAgent(
            instructions: "You are an AI assistant that helps people find information.",
            tools: [AIFunctionFactory.Create(GetDateTime, name: nameof(GetDateTime))]);

Step 2: Create Your Agent Run Middleware

Next, create a function that will get invoked for each agent run. It allows you to inspect the input and output from the agent.

Unless the intention is to use the middleware to stop executing the run, the function should call RunAsync on the provided innerAgent.

This sample middleware just inspects the input and output from the agent run and outputs the number of messages passed into and out of the agent.

using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;

async Task<AgentResponse> CustomAgentRunMiddleware(
    IEnumerable<ChatMessage> messages,
    AgentThread? thread,
    AgentRunOptions? options,
    AIAgent innerAgent,
    CancellationToken cancellationToken)
{
    Console.WriteLine($"Input: {messages.Count()}");
    var response = await innerAgent.RunAsync(messages, thread, options, cancellationToken).ConfigureAwait(false);
    Console.WriteLine($"Output: {response.Messages.Count}");
    return response;
}