.NET: feat(AgentSkills): add IncludeSkillInstructions option to AgentSkills…

dotnet/src/Microsoft.Agents.AI/Skills/AgentSkillsProvider.cs

@@ -1,4 +1,4 @@
-// Copyright (c) Microsoft. All rights reserved.
+// Copyright (c) Microsoft. All rights reserved.
 
 using System;
 using System.Collections.Generic;
@@ -162,7 +162,7 @@ public AgentSkillsProvider(AgentSkillsSource source, AgentSkillsProviderOptions?
         this._options = options;
         this._logger = (loggerFactory ?? NullLoggerFactory.Instance).CreateLogger<AgentSkillsProvider>();
 
-        if (options?.SkillsInstructionPrompt is string prompt)
+        if ((options?.IncludeSkillInstructions ?? true) && options?.SkillsInstructionPrompt is string prompt)
         {
             ValidatePromptTemplate(prompt, nameof(options));
         }
@@ -260,6 +260,11 @@ private IList<AIFunction> BuildTools(IList<AgentSkill> skills, bool hasScripts,
 
     private string? BuildSkillsInstructions(IList<AgentSkill> skills, bool includeScriptInstructions, bool includeResourceInstructions)
     {
+        if (this._options?.IncludeSkillInstructions == false)
+        {
+            return null;
+        }
+
         string promptTemplate = this._options?.SkillsInstructionPrompt ?? DefaultSkillsInstructionPrompt;
 
         var sb = new StringBuilder();

dotnet/src/Microsoft.Agents.AI/Skills/AgentSkillsProviderBuilder.cs

@@ -1,4 +1,4 @@
-// Copyright (c) Microsoft. All rights reserved.
+// Copyright (c) Microsoft. All rights reserved.
 
 using System;
 using System.Collections.Generic;
@@ -139,6 +139,17 @@ public AgentSkillsProviderBuilder UseScriptApproval(bool enabled = true)
         return this;
     }
 
+    /// <summary>
+    /// Enables or disables including skill instructions in the system prompt.
+    /// </summary>
+    /// <param name="enabled">Whether to include skill instructions. Defaults to <see langword="true"/>.</param>
+    /// <returns>This builder instance for chaining.</returns>
+    public AgentSkillsProviderBuilder IncludeSkillInstructions(bool enabled = true)
+    {
+        this.GetOrCreateOptions().IncludeSkillInstructions = enabled;
+        return this;
+    }
+
     /// <summary>
     /// Sets the runner for file-based skill scripts.
     /// </summary>

dotnet/src/Microsoft.Agents.AI/Skills/AgentSkillsProviderOptions.cs

@@ -1,4 +1,4 @@
-// Copyright (c) Microsoft. All rights reserved.
+// Copyright (c) Microsoft. All rights reserved.
 
 using System.Diagnostics.CodeAnalysis;
 using Microsoft.Shared.DiagnosticIds;
@@ -34,4 +34,12 @@ public sealed class AgentSkillsProviderOptions
     /// Set to <see langword="true"/> to rebuild tools and instructions on every invocation.
     /// </summary>
     public bool DisableCaching { get; set; }
+
+    /// <summary>
+    /// Gets or sets a value indicating whether skill instructions should be included in the system prompt.
+    /// When <see langword="true"/> (the default), skill names and descriptions are added
+    /// to the system prompt to guide the model on when to use specific skills.
+    /// Set to <see langword="false"/> to skip including these instructions in the prompt.
+    /// </summary>
+    public bool IncludeSkillInstructions { get; set; } = true;
 }

dotnet/tests/Microsoft.Agents.AI.UnitTests/AgentSkills/AgentSkillsProviderBuilderTests.cs

@@ -1,4 +1,4 @@
-// Copyright (c) Microsoft. All rights reserved.
+// Copyright (c) Microsoft. All rights reserved.
 
 using System;
 using System.Collections.Generic;
@@ -182,6 +182,23 @@ public void Build_UseOptions_ConfiguresOptions()
         Assert.NotNull(provider);
     }
 
+    [Fact]
+    public void Build_IncludeSkillInstructions_ConfiguresOptions()
+    {
+        // Arrange
+        var source = new TestAgentSkillsSource(
+            new TestAgentSkill("test", "Test", "Instructions."));
+
+        // Act
+        var provider = new AgentSkillsProviderBuilder()
+            .UseSource(source)
+            .IncludeSkillInstructions(false)
+            .Build();
+
+        // Assert
+        Assert.NotNull(provider);
+    }
+
     [Fact]
     public async Task Build_WithMultipleCustomSources_AggregatesAllAsync()
     {

dotnet/tests/Microsoft.Agents.AI.UnitTests/AgentSkills/AgentSkillsProviderTests.cs

@@ -1,4 +1,4 @@
-// Copyright (c) Microsoft. All rights reserved.
+// Copyright (c) Microsoft. All rights reserved.
 
 using System;
 using System.Collections.Generic;
@@ -851,6 +851,42 @@ public async Task Constructor_InlineSkills_DeduplicatesAsync()
         Assert.Contains("First instructions.", content!.ToString()!);
     }
 
+    [Fact]
+    public async Task InvokingAsync_IncludeSkillInstructionsFalse_ReturnsNullInstructionsAsync()
+    {
+        // Arrange
+        this.CreateSkill("skip-skill", "Skip test", "Body.");
+        var options = new AgentSkillsProviderOptions { IncludeSkillInstructions = false };
+        var provider = new AgentSkillsProvider(new AgentFileSkillsSource(this._testRoot, s_noOpExecutor), options);
+        var inputContext = new AIContext { Instructions = "Base instructions" };
+        var invokingContext = new AIContextProvider.InvokingContext(this._agent, session: null, inputContext);
+
+        // Act
+        var result = await provider.InvokingAsync(invokingContext, CancellationToken.None);
+
+        // Assert
+        Assert.Equal("Base instructions", result.Instructions); // Should not have changed
+        Assert.NotNull(result.Tools);
+        Assert.Contains(result.Tools!, t => t.Name == "load_skill");
+    }
+
+    [Fact]
+    public void Constructor_IncludeSkillInstructionsFalse_SkipsPromptValidation()
+    {
+        // Arrange — invalid prompt (missing placeholders)
+        var options = new AgentSkillsProviderOptions
+        {
+            IncludeSkillInstructions = false,
+            SkillsInstructionPrompt = "Invalid prompt without placeholders"
+        };
+
+        // Act — should not throw
+        var provider = new AgentSkillsProvider(new AgentFileSkillsSource(this._testRoot, s_noOpExecutor), options);
+
+        // Assert
+        Assert.NotNull(provider);
+    }
+
     /// <summary>
     /// A test skill source that counts how many times <see cref="GetSkillsAsync"/> is called.
     /// </summary>