[Capability] Check tool names against the spec's 128-character limit and character set

CHANGELOG.md

@@ -14,6 +14,7 @@ All notable changes to `mcp/sdk` will be documented in this file.
 * Fix `InMemorySessionStore::exists()` reporting a session past its TTL as existing, while `read()` already treated it as gone.
 * Fix `Psr16NotificationBus` subscribers missing the notifications published after the bus stayed quiet for longer than its TTL: the sequence counter no longer expires, and a subscriber whose cursor is ahead of a lost counter reads what the bus holds.
 * Fix `Session::save()` wiping the other keys of a session that the store failed to read, e.g. when `Psr16SessionStore` hits a cache error: it now returns `false` instead of writing the changed keys alone.
+* Fix tool name validation not following the spec's rule (1 to 128 characters of `A-Z`, `a-z`, `0-9`, `_`, `-` and `.`): names of 65 to 128 characters no longer log a warning, while names with a `/` or a trailing newline now do.
 * Add `Psr6SessionStore` and `Psr6NotificationBus`, which work like `Psr16SessionStore` and `Psr16NotificationBus` over a PSR-6 cache pool. `Builder::setDiscovery()` also accepts a PSR-6 pool as `$cache`.
 
 ### Client

src/Capability/Registry.php

@@ -119,7 +119,7 @@ public function registerTool(Tool $tool, callable|array|string $handler): ToolRe
     {
         if (!$this->nameValidator->isValid($tool->name)) {
             $this->logger->warning(
-                \sprintf('Tool name "%s" is invalid. Tool names should only contain letters (a-z, A-Z), numbers, dots, hyphens, underscores, and forward slashes.', $tool->name),
+                \sprintf('Tool name "%s" is invalid. Tool names should be 1 to 128 characters long and only contain letters (a-z, A-Z), numbers, dots, hyphens and underscores.', $tool->name),
             );
         }
 

src/Capability/Tool/NameValidator.php

@@ -15,6 +15,6 @@ final class NameValidator
 {
     public function isValid(string $name): bool
     {
-        return 1 === preg_match('/^[a-zA-Z0-9._\/-]{1,64}$/', $name);
+        return 1 === preg_match('/^[a-zA-Z0-9._-]{1,128}$/D', $name);
     }
 }

tests/Unit/Capability/Tool/NameValidatorTest.php

@@ -30,9 +30,9 @@ public static function provideValidNames(): array
             ['MyTool123'],
             ['my.tool'],
             ['my-tool'],
-            ['my/tool'],
             ['my_tool-01.02'],
             ['my_long_toolname_that_is_exactly_sixty_four_characters_long_1234'],
+            [str_repeat('a', 128)],
         ];
     }
 
@@ -50,7 +50,9 @@ public static function provideInvalidNames(): array
             ['my@tool'],
             ['my!tool'],
             ['my_tool#1'],
-            ['this_tool_name_is_way_too_long_because_it_exceeds_the_sixty_four_character_limit_set_by_the_validator'],
+            ['my/tool'],
+            ["my_tool\n"],
+            [str_repeat('a', 129)],
         ];
     }
 }