.NET: Remove resource/script placeholder requirement from custom skill templates

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

@@ -40,16 +40,6 @@ public sealed partial class AgentSkillsProvider : AIContextProvider
     /// </summary>
     private const string SkillsPlaceholder = "{skills}";
 
-    /// <summary>
-    /// Placeholder token for the script instructions in the prompt template.
-    /// </summary>
-    private const string ScriptInstructionsPlaceholder = "{script_instructions}";
-
-    /// <summary>
-    /// Placeholder token for the resource instructions in the prompt template.
-    /// </summary>
-    private const string ResourceInstructionsPlaceholder = "{resource_instructions}";
-
     private const string DefaultSkillsInstructionPrompt =
         """
         You have access to skills containing domain-specific knowledge and capabilities.
@@ -62,8 +52,9 @@ You have access to skills containing domain-specific knowledge and capabilities.
         When a task aligns with a skill's domain, follow these steps in exact order:
         - Use `load_skill` to retrieve the skill's instructions.
         - Follow the provided guidance.
-        {resource_instructions}
-        {script_instructions}
+        - Use `read_skill_resource` to read any referenced resources, using the name exactly as listed
+           (e.g. `"style-guide"` not `"style-guide.md"`, `"references/FAQ.md"` not `"FAQ.md"`).
+        - Use `run_skill_script` to run referenced scripts, using the name exactly as listed.
         Only load what is needed, when it is needed.
         """;
 
@@ -258,18 +249,8 @@ private IList<AIFunction> BuildTools(IList<AgentSkill> skills)
             sb.AppendLine("  </skill>");
         }
 
-        const string ResourceInstruction =
-            """
-            - Use `read_skill_resource` to read any referenced resources, using the name exactly as listed
-               (e.g. `"style-guide"` not `"style-guide.md"`, `"references/FAQ.md"` not `"FAQ.md"`).
-            """;
-
-        const string ScriptInstruction = "- Use `run_skill_script` to run referenced scripts, using the name exactly as listed.";
-
         return new StringBuilder(promptTemplate)
             .Replace(SkillsPlaceholder, sb.ToString().TrimEnd())
-            .Replace(ResourceInstructionsPlaceholder, ResourceInstruction)
-            .Replace(ScriptInstructionsPlaceholder, ScriptInstruction)
             .ToString();
     }
 
@@ -378,20 +359,6 @@ private static void ValidatePromptTemplate(string template, string paramName)
                 $"The custom prompt template must contain the '{SkillsPlaceholder}' placeholder for the generated skills list.",
                 paramName);
         }
-
-        if (template.IndexOf(ResourceInstructionsPlaceholder, StringComparison.Ordinal) < 0)
-        {
-            throw new ArgumentException(
-                $"The custom prompt template must contain the '{ResourceInstructionsPlaceholder}' placeholder for resource instructions.",
-                paramName);
-        }
-
-        if (template.IndexOf(ScriptInstructionsPlaceholder, StringComparison.Ordinal) < 0)
-        {
-            throw new ArgumentException(
-                $"The custom prompt template must contain the '{ScriptInstructionsPlaceholder}' placeholder for script instructions.",
-                paramName);
-        }
     }
 
     [LoggerMessage(LogLevel.Information, "Loading skill: {SkillName}")]

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

@@ -134,9 +134,7 @@ public AgentSkillsProviderBuilder UseSource(AgentSkillsSource source)
     /// <summary>
     /// Sets a custom system prompt template.
     /// </summary>
-    /// <param name="promptTemplate">The prompt template with <c>{skills}</c> placeholder for the skills list,
-    /// <c>{resource_instructions}</c> for optional resource instructions,
-    /// and <c>{script_instructions}</c> for optional script instructions.</param>
+    /// <param name="promptTemplate">The prompt template with <c>{skills}</c> placeholder for the skills list.</param>
     /// <returns>This builder instance for chaining.</returns>
     public AgentSkillsProviderBuilder UsePromptTemplate(string promptTemplate)
     {

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

@@ -13,9 +13,7 @@ public sealed class AgentSkillsProviderOptions
 {
     /// <summary>
     /// Gets or sets a custom system prompt template for advertising skills.
-    /// The template must contain <c>{skills}</c> as the placeholder for the generated skills list,
-    /// <c>{resource_instructions}</c> for resource instructions,
-    /// and <c>{script_instructions}</c> for script instructions.
+    /// The template must contain <c>{skills}</c> as the placeholder for the generated skills list.
     /// When <see langword="null"/>, a default template is used.
     /// </summary>
     public string? SkillsInstructionPrompt { get; set; }

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

@@ -159,7 +159,7 @@ public void Build_FluentChaining_ReturnsSameBuilder()
         var result = builder
             .UseSource(source)
             .UseScriptApproval(false)
-            .UsePromptTemplate("Skills:\n{skills}\n{resource_instructions}\n{script_instructions}");
+            .UsePromptTemplate("Skills:\n{skills}");
 
         // Assert
         Assert.Same(builder, result);

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

@@ -100,7 +100,7 @@ public async Task InvokingCoreAsync_CustomPromptTemplate_UsesCustomTemplateAsync
         this.CreateSkill("custom-prompt-skill", "Custom prompt", "Body.");
         var options = new AgentSkillsProviderOptions
         {
-            SkillsInstructionPrompt = "Custom template: {skills}\n{resource_instructions}\n{script_instructions}"
+            SkillsInstructionPrompt = "Custom template: {skills}"
         };
         var provider = new AgentSkillsProvider(new AgentFileSkillsSource(this._testRoot, s_noOpExecutor), options);
         var inputContext = new AIContext();
@@ -122,7 +122,7 @@ public void Constructor_PromptWithoutSkillsPlaceholder_ThrowsArgumentException()
         // Arrange
         var options = new AgentSkillsProviderOptions
         {
-            SkillsInstructionPrompt = "No skills placeholder here {resource_instructions} {script_instructions}"
+            SkillsInstructionPrompt = "No skills placeholder here"
         };
 
         // Act & Assert
@@ -133,28 +133,12 @@ public void Constructor_PromptWithoutSkillsPlaceholder_ThrowsArgumentException()
     }
 
     [Fact]
-    public void Constructor_PromptWithoutRunnerInstructionsPlaceholder_ThrowsArgumentException()
+    public void Constructor_PromptWithOnlySkillsPlaceholder_Succeeds()
     {
         // Arrange
         var options = new AgentSkillsProviderOptions
         {
-            SkillsInstructionPrompt = "Has skills {skills} but no runner instructions {resource_instructions}"
-        };
-
-        // Act & Assert
-        var ex = Assert.Throws<ArgumentException>(() =>
-            new AgentSkillsProvider(new AgentFileSkillsSource(this._testRoot, s_noOpExecutor), options));
-        Assert.Contains("{script_instructions}", ex.Message);
-        Assert.Equal("options", ex.ParamName);
-    }
-
-    [Fact]
-    public void Constructor_PromptWithBothPlaceholders_Succeeds()
-    {
-        // Arrange
-        var options = new AgentSkillsProviderOptions
-        {
-            SkillsInstructionPrompt = "Skills: {skills}\nResources: {resource_instructions}\nRunner: {script_instructions}"
+            SkillsInstructionPrompt = "Skills: {skills}"
         };
 
         // Act — should not throw
@@ -165,19 +149,25 @@ public void Constructor_PromptWithBothPlaceholders_Succeeds()
     }
 
     [Fact]
-    public void Constructor_PromptWithoutResourceInstructionsPlaceholder_ThrowsArgumentException()
+    public async Task InvokingCoreAsync_CustomTemplateWithLegacyPlaceholders_RendersThemLiterallyAsync()
     {
-        // Arrange
+        // Arrange — template contains legacy placeholder tokens that are no longer substituted
+        this.CreateSkill("literal-test-skill", "Literal test", "Body.");
         var options = new AgentSkillsProviderOptions
         {
-            SkillsInstructionPrompt = "Has skills {skills} and runner {script_instructions} but no resource instructions"
+            SkillsInstructionPrompt = "Skills: {skills}\nRes: {resource_instructions}\nScript: {script_instructions}"
         };
+        var provider = new AgentSkillsProvider(new AgentFileSkillsSource(this._testRoot, s_noOpExecutor), options);
+        var inputContext = new AIContext();
+        var invokingContext = new AIContextProvider.InvokingContext(this._agent, session: null, inputContext);
 
-        // Act & Assert
-        var ex = Assert.Throws<ArgumentException>(() =>
-            new AgentSkillsProvider(new AgentFileSkillsSource(this._testRoot, s_noOpExecutor), options));
-        Assert.Contains("{resource_instructions}", ex.Message);
-        Assert.Equal("options", ex.ParamName);
+        // Act
+        var result = await provider.InvokingAsync(invokingContext, CancellationToken.None);
+
+        // Assert — legacy tokens render literally, not substituted
+        Assert.NotNull(result.Instructions);
+        Assert.Contains("{resource_instructions}", result.Instructions);
+        Assert.Contains("{script_instructions}", result.Instructions);
     }
 
     [Fact]