custom-agents

Custom Agents

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

Microsoft Agent Framework supports building custom agents by inheriting from the AIAgent class and implementing the required methods.

This article shows how to build a simple custom agent that parrots back user input in upper case. In most cases building your own agent will involve more complex logic and integration with an AI service.

Getting Started

Add the required NuGet packages to your project.

dotnet add package Microsoft.Agents.AI.Abstractions --prerelease

Create a Custom Agent

The Agent Session

To create a custom agent you also need a session, which is used to keep track of the state of a single conversation, including message history, and any other state the agent needs to maintain.

To make it easy to get started, you can inherit from various base classes that implement common session storage mechanisms.

1. InMemoryAgentSession - stores the chat history in memory and can be serialized to JSON.
2. ServiceIdAgentSession - doesn't store any chat history, but allows you to associate an ID with the session, under which the chat history can be stored externally.

For this example, you'll use the InMemoryAgentSession as the base class for the custom session.

internal sealed class CustomAgentSession : InMemoryAgentSession
{
    internal CustomAgentSession() : base() { }
    internal CustomAgentSession(JsonElement serializedSessionState, JsonSerializerOptions? jsonSerializerOptions = null)
        : base(serializedSessionState, jsonSerializerOptions) { }
}

The Agent class

Next, create the agent class itself by inheriting from the AIAgent class.

internal sealed class UpperCaseParrotAgent : AIAgent
{
}

Constructing sessions

Sessions are always created via two factory methods on the agent class. This allows for the agent to control how sessions are created and deserialized. Agents can therefore attach any additional state or behaviors needed to the session when constructed.