refactor(tools): Convert LangExtractToolConfig to dataclass

Use @DataClass from the standard library instead of a manual __init__,
reducing boilerplate and making the config class more concise and
idiomatic Python.

Author: its-animay

src/google/adk_community/tools/langextract_tool.py

@@ -15,6 +15,8 @@
 from __future__ import annotations
 
 import asyncio
+from dataclasses import dataclass
+from dataclasses import field
 import logging
 from typing import Any
 from typing import Optional
@@ -178,31 +180,20 @@ async def run_async(
       return {'error': f'Extraction failed: {e}'}
 
 
+@dataclass
 class LangExtractToolConfig:
-  """Configuration dataclass for LangExtractTool."""
-
-  def __init__(
-      self,
-      *,
-      name: str = 'langextract',
-      description: str = (
-          'Extracts structured information from unstructured text.'
-      ),
-      examples: Optional[list[lx.data.ExampleData]] = None,
-      model_id: str = 'gemini-2.5-flash',
-      api_key: Optional[str] = None,
-      extraction_passes: int = 1,
-      max_workers: int = 1,
-      max_char_buffer: int = 4000,
-  ):
-    self.name = name
-    self.description = description
-    self.examples = examples or []
-    self.model_id = model_id
-    self.api_key = api_key
-    self.extraction_passes = extraction_passes
-    self.max_workers = max_workers
-    self.max_char_buffer = max_char_buffer
+  """Configuration for LangExtractTool."""
+
+  name: str = 'langextract'
+  description: str = (
+      'Extracts structured information from unstructured text.'
+  )
+  examples: list[lx.data.ExampleData] = field(default_factory=list)
+  model_id: str = 'gemini-2.5-flash'
+  api_key: Optional[str] = None
+  extraction_passes: int = 1
+  max_workers: int = 1
+  max_char_buffer: int = 4000
 
   def build(self) -> LangExtractTool:
     """Instantiate a LangExtractTool from this config."""