Add title field to Prompt for MCP spec compliance

The MCP 2025-11-25 specification defines an optional `title` property on
Prompt for human-readable display in UI contexts, distinct from the
programmatic `name` identifier. This was missing from the SDK.

BC Break: Builder::addPrompt() signature changed — $title parameter added
between $name and $description. Callers using positional arguments for
$description must switch to named arguments.

Closes #276

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: chr-hertel

CHANGELOG.md

@@ -9,6 +9,8 @@ All notable changes to `mcp/sdk` will be documented in this file.
 * Add client component for building MCP clients
 * Add `Builder::setReferenceHandler()` to allow custom `ReferenceHandlerInterface` implementations (e.g. authorization decorators)
 * Add elicitation enum schema types per SEP-1330: `TitledEnumSchemaDefinition`, `MultiSelectEnumSchemaDefinition`, `TitledMultiSelectEnumSchemaDefinition`
+* Add optional `title` field to `Prompt` and `McpPrompt` for MCP spec compliance
+* **BC Break**: `Builder::addPrompt()` signature changed — `$title` parameter added between `$name` and `$description`. Callers using positional arguments for `$description` must switch to named arguments.
 
 0.4.0
 -----

docs/server-builder.md

@@ -352,6 +352,7 @@ $server = Server::builder()
 
 - `handler` (callable|string): The prompt handler
 - `name` (string|null): Optional prompt name
+- `title` (string|null): Optional human-readable title for display in UI
 - `description` (string|null): Optional prompt description
 - `icons` (Icon[]|null): Optional array of icons for the prompt
 

src/Capability/Attribute/McpPrompt.php

@@ -24,12 +24,14 @@ class McpPrompt
 {
     /**
      * @param ?string               $name        overrides the prompt name (defaults to method name)
+     * @param ?string               $title       Optional human-readable title for display in UI
      * @param ?string               $description Optional description of the prompt. Defaults to method DocBlock summary.
      * @param ?Icon[]               $icons       Optional list of icon URLs representing the prompt
      * @param ?array<string, mixed> $meta        Optional metadata
      */
     public function __construct(
         public ?string $name = null,
+        public ?string $title = null,
         public ?string $description = null,
         public ?array $icons = null,
         public ?array $meta = null,

src/Capability/Discovery/Discoverer.php

@@ -271,7 +271,7 @@ private function processMethod(\ReflectionMethod $method, array &$discoveredCoun
                         $paramTag = $paramTags['$'.$param->getName()] ?? null;
                         $arguments[] = new PromptArgument($param->getName(), $paramTag ? trim((string) $paramTag->getDescription()) : null, !$param->isOptional() && !$param->isDefaultValueAvailable());
                     }
-                    $prompt = new Prompt($name, $description, $arguments, $instance->icons, $instance->meta);
+                    $prompt = new Prompt($name, $instance->title, $description, $arguments, $instance->icons, $instance->meta);
                     $completionProviders = $this->getCompletionProviders($method);
                     $prompts[$name] = new PromptReference($prompt, [$className, $methodName], false, $completionProviders);
                     ++$discoveredCount['prompts'];

src/Capability/Registry/Loader/ArrayLoader.php

@@ -252,6 +252,7 @@ public function load(RegistryInterface $registry): void
                 }
                 $prompt = new Prompt(
                     name: $name,
+                    title: $data['title'] ?? null,
                     description: $description,
                     arguments: $arguments,
                     icons: $data['icons'] ?? null,

src/Schema/Prompt.php

@@ -21,6 +21,7 @@
  *
  * @phpstan-type PromptData array{
  *     name: string,
+ *     title?: string,
  *     description?: string,
  *     arguments?: PromptArgumentData[],
  *     icons?: IconData[],
@@ -33,13 +34,15 @@ class Prompt implements \JsonSerializable
 {
     /**
      * @param string                $name        the name of the prompt or prompt template
+     * @param ?string               $title       Optional human-readable title for display in UI
      * @param ?string               $description an optional description of what this prompt provides
      * @param ?PromptArgument[]     $arguments   A list of arguments for templating. Null if not a template.
      * @param ?Icon[]               $icons       optional icons representing the prompt
      * @param ?array<string, mixed> $meta        Optional metadata
      */
     public function __construct(
         public readonly string $name,
+        public readonly ?string $title = null,
         public readonly ?string $description = null,
         public readonly ?array $arguments = null,
         public readonly ?array $icons = null,
@@ -73,6 +76,7 @@ public static function fromArray(array $data): self
 
         return new self(
             name: $data['name'],
+            title: $data['title'] ?? null,
             description: $data['description'] ?? null,
             arguments: $arguments,
             icons: isset($data['icons']) && \is_array($data['icons']) ? array_map(Icon::fromArray(...), $data['icons']) : null,
@@ -83,6 +87,7 @@ public static function fromArray(array $data): self
     /**
      * @return array{
      *     name: string,
+     *     title?: string,
      *     description?: string,
      *     arguments?: array<PromptArgument>,
      *     icons?: Icon[],
@@ -92,6 +97,9 @@ public static function fromArray(array $data): self
     public function jsonSerialize(): array
     {
         $data = ['name' => $this->name];
+        if (null !== $this->title) {
+            $data['title'] = $this->title;
+        }
         if (null !== $this->description) {
             $data['description'] = $this->description;
         }

src/Server/Builder.php

@@ -472,11 +472,12 @@ public function addResourceTemplate(
     public function addPrompt(
         \Closure|array|string $handler,
         ?string $name = null,
+        ?string $title = null,
         ?string $description = null,
         ?array $icons = null,
         ?array $meta = null,
     ): self {
-        $this->prompts[] = compact('handler', 'name', 'description', 'icons', 'meta');
+        $this->prompts[] = compact('handler', 'name', 'title', 'description', 'icons', 'meta');
 
         return $this;
     }

tests/Conformance/server.php

@@ -58,10 +58,10 @@
     ->addResourceTemplate([Elements::class, 'resourceTemplate'], 'test://template/{id}/data', 'template', 'A resource template with parameter substitution', 'application/json')
     ->addResource(static fn () => 'Watched resource content', 'test://watched-resource', 'watched-resource', 'A resource that can be watched')
     // Prompts
-    ->addPrompt(static fn () => [['role' => 'user', 'content' => 'This is a simple prompt for testing.']], 'test_simple_prompt', 'A simple prompt without arguments')
-    ->addPrompt([Elements::class, 'promptWithArguments'], 'test_prompt_with_arguments', 'A prompt with required arguments')
-    ->addPrompt([Elements::class, 'promptWithEmbeddedResource'], 'test_prompt_with_embedded_resource', 'A prompt that includes an embedded resource')
-    ->addPrompt([Elements::class, 'promptWithImage'], 'test_prompt_with_image', 'A prompt that includes image content')
+    ->addPrompt(static fn () => [['role' => 'user', 'content' => 'This is a simple prompt for testing.']], name: 'test_simple_prompt', description: 'A simple prompt without arguments')
+    ->addPrompt([Elements::class, 'promptWithArguments'], name: 'test_prompt_with_arguments', description: 'A prompt with required arguments')
+    ->addPrompt([Elements::class, 'promptWithEmbeddedResource'], name: 'test_prompt_with_embedded_resource', description: 'A prompt that includes an embedded resource')
+    ->addPrompt([Elements::class, 'promptWithImage'], name: 'test_prompt_with_image', description: 'A prompt that includes image content')
     ->build();
 
 $response = $server->run($transport);