fix(skill): update descriptions and improve error handling in generate_image script

skills/nano-banana-pro-openrouter/SKILL.md

@@ -1,6 +1,6 @@
 ---
 name: nano-banana-pro-openrouter
-description: Generate or edit images via OpenRouter using openai-python with the Gemini 3 Pro Image model. Use for prompt-only image generation, image edits, and multi-image compositing; supports 1K/2K/4K output, saves results to the current working directory, and prints MEDIA lines.
+description: 'Generate or edit images via OpenRouter with the Gemini 3 Pro Image model. Use for prompt-only image generation, image edits, and multi-image compositing; supports 1K/2K/4K output, saves results to the current working directory, and prints MEDIA lines.'
 metadata:
   emoji: 🍌
   requires:
@@ -11,11 +11,12 @@ metadata:
   primaryEnv: OPENROUTER_API_KEY
 ---
 
+
 # Nano Banana Pro OpenRouter
 
 ## Overview
 
-Generate or edit images with OpenRouter using the `google/gemini-3-pro-image-preview` model and the openai-python client. Support prompt-only generation, single-image edits, and multi-image composition. Save results to the current working directory and output MEDIA lines for easy attachment.
+Generate or edit images with OpenRouter using the `google/gemini-3-pro-image-preview` model. Support prompt-only generation, single-image edits, and multi-image composition. Save results to the current working directory and output MEDIA lines for easy attachment.
 
 ### Prompt-only generation
 
@@ -58,4 +59,4 @@ The skill reads an optional system prompt from `assets/SYSTEM_TEMPLATE`. This al
 - Read the API key from `OPENROUTER_API_KEY` (no CLI flag).
 - Accept up to 3 input images via repeated `--input-image`.
 - Save output in the current working directory. If multiple images are returned, append `-1`, `-2`, etc.
-- Print `MEDIA: <path>` for each saved image. Do not read images back into the response.
+- Print `MEDIA: <path>` for each saved image. Do not read images back into the response.

skills/nano-banana-pro-openrouter/scripts/generate_image.py

@@ -3,7 +3,6 @@
 # requires-python = ">=3.10"
 # dependencies = [
 #     "openai",
-#     "pillow",
 # ]
 # ///
 """
@@ -32,9 +31,11 @@ def parse_args():
     parser.add_argument("--prompt", required=True, help="Prompt describing the desired image.")
     parser.add_argument("--filename", required=True, help="Output filename (relative to CWD).")
     parser.add_argument(
-        "--resolution",
-        default="1K",
-        help="Output resolution: 1K, 2K, or 4K.",
+      "--resolution",
+      type=str.upper,
+      choices=["1K", "2K", "4K"],
+      default="1K",
+      help="Output resolution: 1K, 2K, or 4K.",
     )
     parser.add_argument(
         "--input-image",
@@ -70,14 +71,16 @@ def build_message_content(prompt: str, input_images):
         content.append({"type": "image_url", "image_url": {"url": data_url}})
     return content
 
-
-def parse_data_url(data_url: str):
-    if not data_url.startswith("data:") or ";base64," not in data_url:
+    def parse_data_url(data_url: str):
+      if not data_url.startswith("data:") or ";base64," not in data_url:
         raise ValueError("Image URL is not a base64 data URL.")
-    header, encoded = data_url.split(",", 1)
-    mime = header[5:].split(";", 1)[0]
-    raw = base64.b64decode(encoded)
-    return mime, raw
+      header, encoded = data_url.split(",", 1)
+      mime = header[5:].split(";", 1)[0]
+      try:
+        raw = base64.b64decode(encoded)
+      except Exception as e:
+        raise SystemExit(f"Failed to decode base64 image payload: {e}")
+      return mime, raw
 
 
 def resolve_output_paths(filename: str, image_count: int, mime: str):
@@ -110,7 +113,7 @@ def load_system_prompt():
     """Load system prompt from assets/SYSTEM_TEMPLATE if it exists and is not empty."""
     script_dir = Path(__file__).parent.parent
     template_path = script_dir / "assets" / "SYSTEM_TEMPLATE"
-    
+
     if template_path.exists():
         content = template_path.read_text().strip()
         if content:
@@ -184,4 +187,4 @@ def main():
 
 
 if __name__ == "__main__":
-    main()
+    main()