fix: use runtime tools for approval auto-approval

- load runtime tools dynamically from Copilot CLI capabilities via tools.list
- merge runtime tools with configured MCP and LSP tools in the approval catalog
- keep a fallback builtin runtime tool list when capabilities are unavailable
- move approval-tool pruning to the app service so dynamic tools are not dropped on load
- update approval UI and docs to use the corrected runtime-tool model

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

sidecar/src/Eryx.AgentHost/Contracts/ProtocolModels.cs

@@ -69,6 +69,13 @@ public sealed class SidecarModelCapabilityDto
     public string? DefaultReasoningEffort { get; init; }
 }
 
+public sealed class SidecarRuntimeToolDto
+{
+    public string Id { get; init; } = string.Empty;
+    public string Label { get; init; } = string.Empty;
+    public string? Description { get; init; }
+}
+
 public sealed class SidecarConnectionDiagnosticsDto
 {
     public string Status { get; init; } = "copilot-error";
@@ -103,6 +110,7 @@ public sealed class SidecarCapabilitiesDto
     public string Runtime { get; init; } = "dotnet-maf";
     public Dictionary<string, SidecarModeCapabilityDto> Modes { get; init; } = new(StringComparer.OrdinalIgnoreCase);
     public IReadOnlyList<SidecarModelCapabilityDto> Models { get; init; } = [];
+    public IReadOnlyList<SidecarRuntimeToolDto> RuntimeTools { get; init; } = [];
     public SidecarConnectionDiagnosticsDto Connection { get; init; } = new();
 }
 

sidecar/src/Eryx.AgentHost/Services/SidecarProtocolHost.cs

@@ -2,6 +2,7 @@ using System.Collections.Concurrent;
 using System.Text.Json;
 using System.Text.Json.Serialization;
 using GitHub.Copilot.SDK;
+using GitHub.Copilot.SDK.Rpc;
 using Eryx.AgentHost.Contracts;
 
 namespace Eryx.AgentHost.Services;
@@ -187,6 +188,7 @@ public sealed class SidecarProtocolHost
     private static async Task<SidecarCapabilitiesDto> BuildCapabilitiesAsync(CancellationToken cancellationToken)
     {
         IReadOnlyList<SidecarModelCapabilityDto> models = [];
+        IReadOnlyList<SidecarRuntimeToolDto> runtimeTools = [];
         CopilotCliContext cliContext;
         SidecarConnectionDiagnosticsDto connection;
         SidecarCopilotCliVersionDiagnosticsDto? cliVersion = null;
@@ -227,6 +229,14 @@ public sealed class SidecarProtocolHost
                 cancellationToken).ConfigureAwait(false);
 
             models = await ListAvailableModelsAsync(client, cancellationToken).ConfigureAwait(false);
+            try
+            {
+                runtimeTools = await ListAvailableRuntimeToolsAsync(client, cancellationToken).ConfigureAwait(false);
+            }
+            catch (Exception exception)
+            {
+                Console.Error.WriteLine($"[eryx sidecar] Failed to list available Copilot runtime tools: {exception.Message}");
+            }
             cliVersion = await cliVersionTask.ConfigureAwait(false);
             connection = CreateReadyConnectionDiagnostics(cliContext.CliPath, models.Count, cliVersion, account);
         }
@@ -241,6 +251,7 @@ public sealed class SidecarProtocolHost
         {
             Modes = BuildModeCapabilities(),
             Models = models,
+            RuntimeTools = runtimeTools,
             Connection = connection,
         };
     }
@@ -284,6 +295,24 @@ public sealed class SidecarProtocolHost
             .ToList();
     }
 
+    private static async Task<IReadOnlyList<SidecarRuntimeToolDto>> ListAvailableRuntimeToolsAsync(
+        CopilotClient client,
+        CancellationToken cancellationToken)
+    {
+        ToolsListResult result = await client.Rpc.Tools.ListAsync(null!, cancellationToken).ConfigureAwait(false);
+        return result.Tools
+            .Where(tool => !string.IsNullOrWhiteSpace(tool.Name))
+            .Select(tool => new SidecarRuntimeToolDto
+            {
+                Id = tool.Name.Trim(),
+                Label = tool.Name.Trim(),
+                Description = string.IsNullOrWhiteSpace(tool.Description) ? null : tool.Description.Trim(),
+            })
+            .DistinctBy(tool => tool.Id, StringComparer.OrdinalIgnoreCase)
+            .OrderBy(tool => tool.Label, StringComparer.OrdinalIgnoreCase)
+            .ToList();
+    }
+
     private static bool IsReasoningEffort(string? value)
     {
         return value is "low" or "medium" or "high" or "xhigh";

sidecar/tests/Eryx.AgentHost.Tests/SidecarProtocolHostTests.cs

@@ -37,6 +37,10 @@ public sealed class SidecarProtocolHostTests
                 JsonElement model = Assert.Single(models);
                 Assert.Equal("gpt-5.4", model.GetProperty("id").GetString());
                 Assert.Equal("medium", model.GetProperty("defaultReasoningEffort").GetString());
+                JsonElement[] runtimeTools = capabilities.GetProperty("runtimeTools").EnumerateArray().ToArray();
+                JsonElement runtimeTool = Assert.Single(runtimeTools);
+                Assert.Equal("web_fetch", runtimeTool.GetProperty("id").GetString());
+                Assert.Equal("web_fetch", runtimeTool.GetProperty("label").GetString());
                 JsonElement connection = capabilities.GetProperty("connection");
                 Assert.Equal("ready", connection.GetProperty("status").GetString());
                 Assert.Equal(@"C:\tools\copilot\copilot.exe", connection.GetProperty("copilotCliPath").GetString());
@@ -403,6 +407,15 @@ public sealed class SidecarProtocolHostTests
                         DefaultReasoningEffort = "medium",
                     },
                 ],
+                RuntimeTools =
+                [
+                    new SidecarRuntimeToolDto
+                    {
+                        Id = "web_fetch",
+                        Label = "web_fetch",
+                        Description = "Fetch content from the web.",
+                    },
+                ],
                 Connection = new SidecarConnectionDiagnosticsDto
                 {
                     Status = "ready",