Add docstring to infer for MCP compatibility

Gradio uses docstring to generate MCP schema (at /gradio_api/mcp/schema) that MCP clients use to get tool desc and arg type and desc

app.py

@@ -35,6 +35,21 @@ def infer(
     num_inference_steps=8,
     progress=gr.Progress(track_tqdm=True),
 ):
+    """Generate an image using Stable Diffusion 3.5 Large TurboX.
+    
+    Args:
+        prompt: The prompt to generate an image from
+        negative_prompt: The negative prompt
+        seed: The generation seed
+        randomize_seed: Whether to randomize the seed
+        width: The width of the generated image in pixels
+        height: The height of the generated image in pixels
+        guidance_scale: How closely the image should align with the prompt
+        num_inference_steps: Number of generation steps
+
+    Returns:
+        The generated image and the seed used for generation as a tuple of (PIL.Image.Image, seed)
+    """
     if randomize_seed:
         seed = random.randint(0, MAX_SEED)