Microsoft 365 Agents SDK (.NET)

Overview

Build enterprise agents for Microsoft 365, Teams, and Copilot Studio using the Microsoft.Agents SDK with ASP.NET Core hosting, agent routing, and MSAL-based authentication.

Before implementation

• Use the microsoft-docs MCP to verify the latest APIs for AddAgent, AgentApplication, and authentication options.
• Confirm package versions in NuGet for the Microsoft.Agents.* packages you plan to use.

Installation

dotnet add package Microsoft.Agents.Hosting.AspNetCore
dotnet add package Microsoft.Agents.Authentication.Msal
dotnet add package Microsoft.Agents.Storage
dotnet add package Microsoft.Agents.CopilotStudio.Client
dotnet add package Microsoft.Identity.Client.Extensions.Msal

Configuration (appsettings.json)

{
  "TokenValidation": {
    "Enabled": true,
    "Audiences": [
      "{{ClientId}}"
    ],
    "TenantId": "{{TenantId}}"
  },
  "AgentApplication": {
    "StartTypingTimer": false,
    "RemoveRecipientMention": false,
    "NormalizeMentions": false
  },
  "Connections": {
    "ServiceConnection": {
      "Settings": {
        "AuthType": "ClientSecret",
        "ClientId": "{{ClientId}}",
        "ClientSecret": "{{ClientSecret}}",
        "AuthorityEndpoint": "https://login.microsoftonline.com/{{TenantId}}",
        "Scopes": [
          "https://api.botframework.com/.default"
        ]
      }
    }
  },
  "ConnectionsMap": [
    {
      "ServiceUrl": "*",
      "Connection": "ServiceConnection"
    }
  ],
  "CopilotStudioClientSettings": {
    "DirectConnectUrl": "",
    "EnvironmentId": "",
    "SchemaName": "",
    "TenantId": "",
    "AppClientId": "",
    "AppClientSecret": ""
  }
}

Core Workflow: ASP.NET Core agent host

using Microsoft.Agents.Builder;
using Microsoft.Agents.Hosting.AspNetCore;
using Microsoft.Agents.Storage;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddHttpClient();
builder.AddAgentApplicationOptions();
builder.AddAgent<MyAgent>();
builder.Services.AddSingleton<IStorage, MemoryStorage>();

builder.Services.AddControllers();
builder.Services.AddAgentAspNetAuthentication(builder.Configuration);

WebApplication app = builder.Build();

app.UseAuthentication();
app.UseAuthorization();

app.MapGet("/", () => "Microsoft Agents SDK Sample");

var incomingRoute = app.MapPost("/api/messages",
    async (HttpRequest request, HttpResponse response, IAgentHttpAdapter adapter, IAgent agent, CancellationToken ct) =>
    {
        await adapter.ProcessAsync(request, response, agent, ct);
    });

if (!app.Environment.IsDevelopment())
{
    incomingRoute.RequireAuthorization();
}
else
{
    app.Urls.Add("http://localhost:3978");
}

app.Run();

AgentApplication routing

using Microsoft.Agents.Builder;
using Microsoft.Agents.Builder.App;
using Microsoft.Agents.Builder.State;
using Microsoft.Agents.Core.Models;
using System;
using System.Threading;
using System.Threading.Tasks;

public sealed class MyAgent : AgentApplication
{
    public MyAgent(AgentApplicationOptions options) : base(options)
    {
        OnConversationUpdate(ConversationUpdateEvents.MembersAdded, WelcomeAsync);
        OnActivity(ActivityTypes.Message, OnMessageAsync, rank: RouteRank.Last);
        OnTurnError(OnTurnErrorAsync);
    }

    private static async Task WelcomeAsync(ITurnContext turnContext, ITurnState turnState, CancellationToken ct)
    {
        foreach (ChannelAccount member in turnContext.Activity.MembersAdded)
        {
            if (member.Id != turnContext.Activity.Recipient.Id)
            {
                await turnContext.SendActivityAsync(
                    MessageFactory.Text("Welcome to the agent."),
                    ct);
            }
        }
    }

    private static async Task OnMessageAsync(ITurnContext turnContext, ITurnState turnState, CancellationToken ct)
    {
        await turnContext.SendActivityAsync(
            MessageFactory.Text($"You said: {turnContext.Activity.Text}"),
            ct);
    }

    private static async Task OnTurnErrorAsync(
        ITurnContext turnContext,
        ITurnState turnState,
        Exception exception,
        CancellationToken ct)
    {
        await turnState.Conversation.DeleteStateAsync(turnContext, ct);

        var endOfConversation = Activity.CreateEndOfConversationActivity();
        endOfConversation.Code = EndOfConversationCodes.Error;
        endOfConversation.Text = exception.Message;
        await turnContext.SendActivityAsync(endOfConversation, ct);
    }
}

Copilot Studio direct-to-engine client

DelegatingHandler for token acquisition (interactive flow)

using System.Net.Http.Headers;
using Microsoft.Agents.CopilotStudio.Client;
using Microsoft.Identity.Client;

internal sealed class AddTokenHandler : DelegatingHand