Remove instructions from base agent type, and ensure description is only required where necessary. (#154)

* Remove instructions from base agent type, and ensure description is only required where necessary.

* Fix code issue.

* Remove unused import.

* Remove typo

* Make the description parameter optional

* Also use name for handoffs if no description is provided.

dotnet/src/Microsoft.Agents.Orchestration/AgentActor.cs

@@ -1,6 +1,5 @@
 // Copyright (c) Microsoft. All rights reserved.
 
-using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Threading;
@@ -30,7 +29,7 @@ public abstract class AgentActor : OrchestrationActor
             id,
             runtime,
             context,
-            VerifyDescription(agent),
+            agent.Description,
             logger)
     {
         this.Agent = agent;
@@ -162,9 +161,4 @@ public abstract class AgentActor : OrchestrationActor
             }
         }
     }
-
-    private static string VerifyDescription(Agent agent)
-    {
-        return agent.Description ?? throw new ArgumentException($"Missing agent description: {agent.Name ?? agent.Id}", nameof(agent));
-    }
 }

dotnet/src/Microsoft.Agents.Orchestration/Handoff/Handoffs.cs

@@ -1,5 +1,6 @@
 // Copyright (c) Microsoft. All rights reserved.
 
+using System;
 using System.Collections.Generic;
 using Microsoft.Extensions.AI.Agents;
 using Microsoft.Extensions.AI.Agents.Runtime;
@@ -84,7 +85,12 @@ public static class OrchestrationHandoffsExtensions
 
         foreach (Agent target in targets)
         {
-            agentHandoffs[target.Name ?? target.Id] = target.Description ?? string.Empty;
+            if (string.IsNullOrWhiteSpace(target.Description) && string.IsNullOrWhiteSpace(target.Name))
+            {
+                throw new InvalidOperationException($"The provided target agent with Id '{target.Id}' has no description or name, and no handoff description has been provided. At least one of these are required to register a handoff so that the appropriate target agent can be chosen.");
+            }
+
+            agentHandoffs[target.Name ?? target.Id] = target.Description ?? target.Name!;
         }
 
         return handoffs;

dotnet/src/Microsoft.Agents.Orchestration/OrchestrationActor.cs

@@ -15,7 +15,7 @@ public abstract class OrchestrationActor : RuntimeActor
     /// <summary>
     /// Initializes a new instance of the <see cref="OrchestrationActor"/> class.
     /// </summary>
-    protected OrchestrationActor(ActorId id, IAgentRuntime runtime, OrchestrationContext context, string description, ILogger? logger = null)
+    protected OrchestrationActor(ActorId id, IAgentRuntime runtime, OrchestrationContext context, string? description = null, ILogger? logger = null)
         : base(id, runtime, description, logger)
     {
         this.Context = context;

dotnet/src/Microsoft.Extensions.AI.Agents.Abstractions/Agent.cs

@@ -15,7 +15,7 @@ namespace Microsoft.Extensions.AI.Agents;
 public abstract class Agent
 {
     /// <summary>
-    /// Gets the identifier of the agent (optional).
+    /// Gets the identifier of the agent.
     /// </summary>
     /// <value>
     /// The identifier of the agent. The default is a random GUID value, but for service agents, it will match the id of the agent in the service.
@@ -32,11 +32,6 @@ public abstract class Agent
     /// </summary>
     public virtual string? Description { get; }
 
-    /// <summary>
-    /// Gets the instructions for the agent (optional).
-    /// </summary>
-    public virtual string? Instructions { get; }
-
     /// <summary>
     /// Get a new <see cref="AgentThread"/> instance that is compatible with the agent.
     /// </summary>

dotnet/src/Microsoft.Extensions.AI.Agents.Runtime.Abstractions/ActorMetadata.cs

@@ -15,7 +15,7 @@ public readonly struct ActorMetadata : IEquatable<ActorMetadata>
     /// <param name="type">The type of the actor.</param>
     /// <param name="key">The unique key associated with the actor.</param>
     /// <param name="description">A brief description of the actor.</param>
-    public ActorMetadata(ActorType type, string key, string description)
+    public ActorMetadata(ActorType type, string key, string? description = null)
     {
         if (!ActorId.IsValidKey(key))
         {
@@ -46,7 +46,7 @@ public readonly struct ActorMetadata : IEquatable<ActorMetadata>
     /// <summary>
     /// A brief description of the actor's purpose or functionality.
     /// </summary>
-    public string Description { get; }
+    public string? Description { get; }
 
     /// <inheritdoc/>
     public override readonly bool Equals(object? obj) =>

dotnet/src/Microsoft.Extensions.AI.Agents.Runtime.Abstractions/RuntimeActor.cs

@@ -53,7 +53,7 @@ public abstract class RuntimeActor : IRuntimeActor
     protected RuntimeActor(
         ActorId id,
         IAgentRuntime runtime,
-        string description,
+        string? description = null,
         ILogger? logger = null)
     {
         this.Id = id;

dotnet/src/Microsoft.Extensions.AI.Agents/ChatCompletion/ChatClientAgent.cs

@@ -56,8 +56,10 @@ public sealed class ChatClientAgent : Agent
     /// <inheritdoc/>
     public override string? Description => this._agentOptions?.Description;
 
-    /// <inheritdoc/>
-    public override string? Instructions => this._agentOptions?.Instructions;
+    /// <summary>
+    /// Gets the instructions for the agent (optional).
+    /// </summary>
+    public string? Instructions => this._agentOptions?.Instructions;
 
     /// <summary>
     /// Gets of the default <see cref="Microsoft.Extensions.AI.ChatOptions"/> used by the agent.