Added Audio to FastMCP (#1130)

src/mcp/server/fastmcp/__init__.py

@@ -3,7 +3,7 @@
 from importlib.metadata import version
 
 from .server import Context, FastMCP
-from .utilities.types import Image
+from .utilities.types import Audio, Image
 
 __version__ = version("mcp")
-__all__ = ["FastMCP", "Context", "Image"]
+__all__ = ["FastMCP", "Context", "Image", "Audio"]

src/mcp/server/fastmcp/utilities/func_metadata.py

@@ -21,7 +21,7 @@ from pydantic_core import PydanticUndefined
 
 from mcp.server.fastmcp.exceptions import InvalidSignature
 from mcp.server.fastmcp.utilities.logging import get_logger
-from mcp.server.fastmcp.utilities.types import Image
+from mcp.server.fastmcp.utilities.types import Audio, Image
 from mcp.types import ContentBlock, TextContent
 
 logger = get_logger(__name__)
@@ -506,6 +506,9 @@ def _convert_to_content(
     if isinstance(result, Image):
         return [result.to_image_content()]
 
+    if isinstance(result, Audio):
+        return [result.to_audio_content()]
+
     if isinstance(result, list | tuple):
         return list(
             chain.from_iterable(

src/mcp/server/fastmcp/utilities/types.py

@@ -3,7 +3,7 @@
 import base64
 from pathlib import Path
 
-from mcp.types import ImageContent
+from mcp.types import AudioContent, ImageContent
 
 
 class Image:
@@ -52,3 +52,50 @@ class Image:
             raise ValueError("No image data available")
 
         return ImageContent(type="image", data=data, mimeType=self._mime_type)
+
+
+class Audio:
+    """Helper class for returning audio from tools."""
+
+    def __init__(
+        self,
+        path: str | Path | None = None,
+        data: bytes | None = None,
+        format: str | None = None,
+    ):
+        if not bool(path) ^ bool(data):
+            raise ValueError("Either path or data can be provided")
+
+        self.path = Path(path) if path else None
+        self.data = data
+        self._format = format
+        self._mime_type = self._get_mime_type()
+
+    def _get_mime_type(self) -> str:
+        """Get MIME type from format or guess from file extension."""
+        if self._format:
+            return f"audio/{self._format.lower()}"
+
+        if self.path:
+            suffix = self.path.suffix.lower()
+            return {
+                ".wav": "audio/wav",
+                ".mp3": "audio/mpeg",
+                ".ogg": "audio/ogg",
+                ".flac": "audio/flac",
+                ".aac": "audio/aac",
+                ".m4a": "audio/mp4",
+            }.get(suffix, "application/octet-stream")
+        return "audio/wav"  # default for raw binary data
+
+    def to_audio_content(self) -> AudioContent:
+        """Convert to MCP AudioContent."""
+        if self.path:
+            with open(self.path, "rb") as f:
+                data = base64.b64encode(f.read()).decode()
+        elif self.data is not None:
+            data = base64.b64encode(self.data).decode()
+        else:
+            raise ValueError("No audio data available")
+
+        return AudioContent(type="audio", data=data, mimeType=self._mime_type)