diff --git a/src/timmy_serve/voice_tts.py b/src/timmy_serve/voice_tts.py
index 251b97f2..c74cdaaa 100644
--- a/src/timmy_serve/voice_tts.py
+++ b/src/timmy_serve/voice_tts.py
@@ -37,6 +37,7 @@ class VoiceTTS:
 
     @property
     def available(self) -> bool:
+        """Whether the TTS engine initialized successfully and can produce audio."""
         return self._available
 
     def speak(self, text: str) -> None:
@@ -68,11 +69,13 @@ class VoiceTTS:
                 logger.error("VoiceTTS: speech failed — %s", exc)
 
     def set_rate(self, rate: int) -> None:
+        """Set speech rate in words per minute (typical range: 100–300, default 175)."""
         self._rate = rate
         if self._engine:
             self._engine.setProperty("rate", rate)
 
     def set_volume(self, volume: float) -> None:
+        """Set speech volume. Value is clamped to the 0.0–1.0 range."""
         self._volume = max(0.0, min(1.0, volume))
         if self._engine:
             self._engine.setProperty("volume", self._volume)
@@ -92,6 +95,7 @@ class VoiceTTS:
             return []
 
     def set_voice(self, voice_id: str) -> None:
+        """Set the active TTS voice by system voice ID (see ``get_voices()``)."""
         if self._engine:
             self._engine.setProperty("voice", voice_id)