feat: Update validate command to support optional manifest argument and improve error handling

Author: asklar

CLI.md

@@ -19,7 +19,7 @@ Options:
 
 Commands:
   init [directory]           Create a new MCPB extension manifest
-  validate <manifest>        Validate a MCPB manifest file
+  validate [manifest]        Validate a MCPB manifest file
   pack <directory> [output]  Pack a directory into a MCPB extension
   sign [options] <mcpb-file>  Sign a MCPB extension file
   verify <mcpb-file>          Verify the signature of a MCPB extension file
@@ -58,7 +58,7 @@ The command will prompt you for:
 
 After creating the manifest, it provides helpful next steps based on your server type.
 
-### `mcpb validate <path>`
+### `mcpb validate [path]`
 
 Validates a MCPB manifest file against the schema. You can provide either a direct path to a manifest.json file or a directory containing one.
 
@@ -69,6 +69,9 @@ mcpb validate manifest.json
 # Validate manifest in directory
 mcpb validate ./my-extension
 mcpb validate .
+
+# Validate using --dirname without specifying manifest.json explicitly
+mcpb validate --dirname ./my-extension
 ```
 
 #### Additional validation with `--dirname`
@@ -79,7 +82,7 @@ Passing `--dirname <directory>` performs deeper checks that require access to th
 - Launches the server (honoring `${__dirname}` tokens) and discovers tools & prompts using the same logic as `mcpb pack`.
 - Compares discovered capability names against the manifest and fails if they differ.
 
-Use `--update` alongside `--dirname` to rewrite the manifest in-place with the discovered tool/prompt lists (including `tools_generated` / `prompts_generated` flags). When rewriting, the CLI also copies over tool descriptions and prompt metadata (descriptions, declared arguments, and prompt text) returned by the server. Without `--update`, any mismatch causes the command to fail.
+When `--dirname` is supplied without an explicit manifest argument, the CLI automatically resolves `<directory>/manifest.json`. Use `--update` alongside `--dirname` to rewrite the manifest in-place with the discovered tool/prompt lists (including `tools_generated` / `prompts_generated` flags). When rewriting, the CLI also copies over tool descriptions and prompt metadata (descriptions, declared arguments, and prompt text) returned by the server. Without `--update`, any mismatch causes the command to fail.
 
 The discovery step respects the same environment overrides as `mcpb pack`:
 

dotnet/README.md

@@ -23,7 +23,7 @@ dotnet tool install --global Mcpb.Cli --add-source ./bin/Release
 | Command                                                                                 | Description                      |
 | --------------------------------------------------------------------------------------- | -------------------------------- |
 | `mcpb init [directory] [--server-type node\|python\|binary\|auto] [--entry-point path]` | Create manifest.json             |
-| `mcpb validate <manifest\|directory>`                                                   | Validate manifest                |
+| `mcpb validate [manifest\|directory]`                                                   | Validate manifest                |
 | `mcpb pack [directory] [output]`                                                        | Create .mcpb archive             |
 | `mcpb unpack <file> [outputDir]`                                                        | Extract archive                  |
 | `mcpb sign <file> [--cert cert.pem --key key.pem --self-signed]`                        | Sign bundle                      |

dotnet/mcpb.Tests/CliValidateTests.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Collections.Generic;
 using System.IO;
 using System.Text.Json;
@@ -48,6 +49,51 @@ public void Validate_ValidManifest_Succeeds()
         Assert.True(string.IsNullOrWhiteSpace(stderr));
     }
 
+    [Fact]
+    public void Validate_WithDirnameOnly_UsesDefaultManifest()
+    {
+        var dir = CreateTempDir();
+        var manifest = new Mcpb.Core.McpbManifest
+        {
+            Name = "ok",
+            Description = "desc",
+            Author = new Mcpb.Core.McpbManifestAuthor { Name = "A" },
+            Server = new Mcpb.Core.McpbManifestServer
+            {
+                Type = "binary",
+                EntryPoint = "server/ok",
+                McpConfig = new Mcpb.Core.McpServerConfigWithOverrides { Command = "${__dirname}/server/ok" }
+            },
+            Tools = new List<Mcpb.Core.McpbManifestTool>
+            {
+                new() { Name = "dummy", Description = "fake" }
+            },
+            Prompts = new List<Mcpb.Core.McpbManifestPrompt>
+            {
+                new() { Name = "prompt1", Description = "desc", Text = "body" }
+            }
+        };
+        Directory.CreateDirectory(Path.Combine(dir, "server"));
+        File.WriteAllText(Path.Combine(dir, "server", "ok"), "binary");
+        File.WriteAllText(Path.Combine(dir, "manifest.json"), JsonSerializer.Serialize(manifest, McpbJsonContext.WriteOptions));
+        Environment.SetEnvironmentVariable("MCPB_TOOL_DISCOVERY_JSON", "[{\"name\":\"dummy\",\"description\":\"fake\"}]");
+        Environment.SetEnvironmentVariable("MCPB_PROMPT_DISCOVERY_JSON", "[{\"name\":\"prompt1\",\"description\":\"desc\",\"text\":\"body\"}]");
+        try
+        {
+            var (code, stdout, stderr) = InvokeCli(dir, "validate", "--dirname", dir);
+            _output.WriteLine("STDOUT: " + stdout);
+            _output.WriteLine("STDERR: " + stderr);
+            Assert.Equal(0, code);
+            Assert.Contains("Manifest is valid!", stdout);
+            Assert.True(string.IsNullOrWhiteSpace(stderr));
+        }
+        finally
+        {
+            Environment.SetEnvironmentVariable("MCPB_TOOL_DISCOVERY_JSON", null);
+            Environment.SetEnvironmentVariable("MCPB_PROMPT_DISCOVERY_JSON", null);
+        }
+    }
+
     [Fact]
     public void Validate_MissingDescription_Fails()
     {

dotnet/mcpb/Commands/ValidateCommand.cs

@@ -12,35 +12,50 @@ public static class ValidateCommand
 {
     public static Command Create()
     {
-        var manifestArg = new Argument<string>("manifest", description: "Path to manifest.json or its directory");
+        var manifestArg = new Argument<string?>("manifest", description: "Path to manifest.json or its directory");
+        manifestArg.Arity = ArgumentArity.ZeroOrOne;
         var dirnameOpt = new Option<string?>("--dirname", description: "Directory containing referenced files and server entry point");
         var updateOpt = new Option<bool>("--update", description: "Update manifest tools/prompts to match discovery results");
         var cmd = new Command("validate", "Validate an MCPB manifest file") { manifestArg, dirnameOpt, updateOpt };
-        cmd.SetHandler(async (string path, string? dirname, bool update) =>
+        cmd.SetHandler(async (string? path, string? dirname, bool update) =>
         {
             if (update && string.IsNullOrWhiteSpace(dirname))
             {
                 Console.Error.WriteLine("ERROR: --update requires --dirname to locate manifest assets.");
                 Environment.ExitCode = 1;
                 return;
             }
-            if (Directory.Exists(path))
+            if (string.IsNullOrWhiteSpace(path))
             {
-                path = Path.Combine(path, "manifest.json");
+                if (!string.IsNullOrWhiteSpace(dirname))
+                {
+                    path = Path.Combine(dirname, "manifest.json");
+                }
+                else
+                {
+                    Console.Error.WriteLine("ERROR: Manifest path or --dirname must be specified.");
+                    Environment.ExitCode = 1;
+                    return;
+                }
+            }
+            var manifestPath = path!;
+            if (Directory.Exists(manifestPath))
+            {
+                manifestPath = Path.Combine(manifestPath, "manifest.json");
             }
-            if (!File.Exists(path))
+            if (!File.Exists(manifestPath))
             {
-                Console.Error.WriteLine($"ERROR: File not found: {path}");
+                Console.Error.WriteLine($"ERROR: File not found: {manifestPath}");
                 Environment.ExitCode = 1;
                 return;
             }
             string json;
             try
             {
-                json = File.ReadAllText(path);
+                json = File.ReadAllText(manifestPath);
                 if (Environment.GetEnvironmentVariable("MCPB_DEBUG_VALIDATE") == "1")
                 {
-                    Console.WriteLine($"DEBUG: Read manifest {path} length={json.Length}");
+                    Console.WriteLine($"DEBUG: Read manifest {manifestPath} length={json.Length}");
                 }
 
                 static void PrintWarnings(IEnumerable<ValidationIssue> warnings, bool toError)
@@ -186,7 +201,7 @@ static void PrintWarnings(IEnumerable<ValidationIssue> warnings, bool toError)
                             var updatedWarnings = updatedIssues.Where(i => i.Severity == ValidationSeverity.Warning).ToList();
                             var updatedManifest = JsonSerializer.Deserialize<McpbManifest>(updatedJson, McpbJsonContext.Default.McpbManifest)!;
 
-                            File.WriteAllText(path, updatedJson);
+                            File.WriteAllText(manifestPath, updatedJson);
 
                             if (updatedErrors.Count > 0)
                             {