Update agent.py

agent.py

@@ -110,9 +110,15 @@ class GeminiModel:
 @tool
 def gaia_file_reader(file_id: str) -> str:
     """
+    Download a GAIA attachment and return its contents.
+
+    Args:
+        file_id: The identifier that appears inside a <file:...> placeholder
+                 in the GAIA question prompt.
+
     Returns:
-        • base64-str for binary files (images, pdf, etc.)
-        • decoded text for utf-8 files
+        A base-64 string for binary files (images, PDF, etc.) or UTF-8 text for
+        plain-text files.
     """
     try:
         raw = _download_file(file_id)