.NET [Breaking]: Remove old MCP skill functionality

dotnet/samples/02-agents/AgentProviders/foundry/Agent_Step26_FoundryToolboxMcpSkills/README.md

@@ -8,7 +8,7 @@ and inject them as `AIContextProviders` so the agent can discover and use them a
 
 - Connecting to a Foundry toolbox's MCP endpoint via Streamable HTTP transport
 - Injecting a fresh Azure AI bearer token (`https://ai.azure.com/.default`) on every MCP request
-- Using `AgentSkillsProviderBuilder.UseMcpSkills(client)` to discover skills from the toolbox
+- Using `AgentSkillsProviderBuilder.UseMcpSkills(client)` to discover skills from the toolbox through `skills/list`
 - Injecting the discovered skills into `AIProjectClient.AsAIAgent(...)` via `AIContextProviders`
 - Auto-approving skill tools with `UseToolApproval` and `AgentSkillsProvider.AllToolsAutoApprovalRule`
 
@@ -19,7 +19,7 @@ for a walkthrough of the full approval flow.
 ## Prerequisites
 
 - A Microsoft Foundry project with a toolbox already configured
-- The toolbox MCP endpoint must expose `skill://index.json` with `skill-md` entries (SEP-2640). If the resource is absent, the sample runs but the skills provider will be empty.
+- The toolbox MCP endpoint must declare the `io.modelcontextprotocol/skills` extension and implement `skills/list` and resource reads for the advertised skills. If the extension is not declared, the skills provider will be empty.
 - An authenticated Azure identity (for example, sign in with `az login`)
 
 Set the following environment variables:

dotnet/samples/02-agents/AgentProviders/foundry/README.md

@@ -74,7 +74,7 @@ Some samples require extra tool-specific environment variables. See each sample
 | [Local MCP](./Agent_Step23_LocalMCP/) | Local MCP client with HTTP transport |
 | [Code interpreter file download](./Agent_Step24_CodeInterpreterFileDownload/) | Download container files generated by code interpreter |
 | [Foundry toolbox via MCP](./Agent_Step25_FoundryToolboxMcp/README.md) | Use a Foundry Toolbox from a non-hosted agent via its MCP endpoint |
-| [Foundry toolbox MCP skills](./Agent_Step26_FoundryToolboxMcpSkills/README.md) | Use a Foundry Toolbox with MCP-based skills discovery (SEP-2640) via AIContextProviders |
+| [Foundry toolbox MCP skills](./Agent_Step26_FoundryToolboxMcpSkills/README.md) | Use a Foundry Toolbox with MCP Skills extension discovery through `skills/list` via AIContextProviders |
 
 ## Running the samples
 
@@ -87,4 +87,3 @@ dotnet run --project .\Agent_Step01_Basics
 
 If you want to exercise the full create-run-delete lifecycle, run `Agent_Step00_FoundryAgentLifecycle`.
 
-

dotnet/src/Microsoft.Agents.AI.Mcp/Skills/AgentMcpSkillResource.cs

@@ -1,7 +1,6 @@
 // Copyright (c) Microsoft. All rights reserved.
 
 using System;
-using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.Extensions.AI;
@@ -12,48 +11,36 @@
 namespace Microsoft.Agents.AI;
 
 /// <summary>
-/// An <see cref="AgentSkillResource"/> backed by content fetched from an MCP server.
+/// A supporting resource for a skill discovered through <c>skills/list</c>.
 /// </summary>
-/// <remarks>
-/// The <see cref="ReadResourceResult"/> is fetched eagerly by <see cref="AgentMcpSkill.GetResourceAsync"/>
-/// at construction time; <see cref="ReadAsync"/> extracts the content from the result.
-/// </remarks>
 internal sealed class AgentMcpSkillResource : AgentSkillResource
 {
-    private readonly ReadResourceResult _result;
+    private readonly ResourceContents _content;
 
     /// <summary>
-    /// Initializes a new instance of the <see cref="AgentMcpSkillResource"/> class with a pre-fetched result.
+    /// Initializes a supporting resource with verified content fetched from the MCP server.
     /// </summary>
-    /// <param name="name">The resource name (e.g. a relative path or identifier).</param>
-    /// <param name="result">The result returned by the MCP server's <c>resources/read</c> request.</param>
+    /// <param name="name">The resource's relative name.</param>
+    /// <param name="content">The resource content that has passed size and digest verification.</param>
     /// <param name="description">An optional description of the resource.</param>
-    public AgentMcpSkillResource(string name, ReadResourceResult result, string? description = null)
+    public AgentMcpSkillResource(string name, ResourceContents content, string? description = null)
         : base(Throw.IfNullOrWhitespace(name), description)
     {
-        this._result = Throw.IfNull(result);
+        this._content = Throw.IfNull(content);
     }
 
     /// <inheritdoc/>
     /// <returns>
-    /// A <see cref="DataContent"/> when the resource contains binary content, a <see cref="string"/> when
-    /// it contains text, or <see langword="null"/> when the server returned no content blocks.
+    /// Binary content as <see cref="DataContent"/>, text as a <see cref="string"/>,
+    /// or <see langword="null"/> for empty text.
     /// </returns>
     public override Task<object?> ReadAsync(IServiceProvider? serviceProvider = null, CancellationToken cancellationToken = default)
     {
-        BlobResourceContents? blob = this._result.Contents.OfType<BlobResourceContents>().FirstOrDefault();
-        if (blob is not null)
+        return Task.FromResult<object?>(this._content switch
         {
-            return Task.FromResult<object?>(blob.ToAIContent());
-        }
-
-        string text = string.Join("\n", this._result.Contents.OfType<TextResourceContents>().Select(c => c.Text));
-
-        if (text.Length == 0)
-        {
-            return Task.FromResult<object?>(null);
-        }
-
-        return Task.FromResult<object?>(text);
+            TextResourceContents text => text.Text.Length == 0 ? null : text.Text,
+            BlobResourceContents binary => binary.ToAIContent(),
+            _ => throw new InvalidOperationException("Unsupported listed skill content."),
+        });
     }
 }