Nano Banana Agent Skill

Nano Banana Image Generation

Generate professional images via the Gemini CLI's nanobanana extension.

When to Use This Skill

ALWAYS use this skill when the user:

• Asks for any image, graphic, illustration, or visual
• Wants a thumbnail, featured image, or banner
• Requests icons, diagrams, or patterns
• Asks to edit, modify, or restore a photo
• Uses words like: generate, create, make, draw, design, visualize

Do NOT attempt to generate images through any other method.

Before First Use

• Verify extension is installed:

   gemini extensions list | grep nanobanana

• If missing, install it:

   gemini extensions install https://github.com/gemini-cli-extensions/nanobanana

• Verify API key is set:

   [ -n "$GEMINI_API_KEY" ] && echo "API key configured" || echo "Missing GEMINI_API_KEY"

Command Selection

| User Request | Command |

|--------------|---------|

| "make me a blog header" | /generate |

| "create an app icon" | /icon |

| "draw a flowchart of..." | /diagram |

| "fix this old photo" | /restore |

| "remove the background" | /edit |

| "create a repeating texture" | /pattern |

| "make a comic strip" | /story |

Available Commands

Note: Always use the --yolo flag to automatically approve all tool actions.

| Command | Use Case |

|---------|----------|

| gemini --yolo "/generate 'prompt'" | Text-to-image generation |

| gemini --yolo "/edit file.png 'instruction'" | Modify existing image |

| gemini --yolo "/restore old_photo.jpg 'fix scratches'" | Repair damaged photos |

| gemini --yolo "/icon 'description'" | App icons, favicons, UI elements |

| gemini --yolo "/diagram 'description'" | Flowcharts, architecture diagrams |

| gemini --yolo "/pattern 'description'" | Seamless textures and patterns |

| gemini --yolo "/story 'description'" | Sequential/narrative images |

| gemini --yolo "/nanobanana prompt" | Natural language interface |

Common Options

• --yolo - Required. Auto-approve all tool actions (no confirmation prompts)
• --count=N - Generate N variations (1-8)
• --preview - Auto-open generated images
• --styles="style1,style2" - Apply artistic styles
• --format=grid|separate - Output arrangement

Common Sizes

| Use Case | Dimensions | Notes |

|----------|------------|-------|

| YouTube thumbnail | 1280x720 | --aspect=16:9 |

| Blog featured image | 1200x630 | Social preview friendly |

| Square social | 1080x1080 | Instagram, LinkedIn |

| Twitter/X header | 1500x500 | Wide banner |

| Vertical story | 1080x1920 | --aspect=9:16 |

Model Selection

Default: gemini-2.5-flash-image (~$0.04/image)

For higher quality (4K, better reasoning):

export NANOBANANA_MODEL=gemini-3-pro-image-preview

Blog Featured Image Examples

# Modern illustration style
gemini --yolo "/generate 'modern flat illustration of developer coding at laptop, purple and blue gradient background, minimalist style, no text' --preview"

# Professional photography style
gemini --yolo "/generate 'professional editorial photo of coffee cup next to laptop on wooden desk, morning sunlight, shallow depth of field, no text' --count=3"

# Tech/abstract
gemini --yolo "/generate 'abstract visualization of neural network connections, dark background with glowing blue nodes, futuristic style' --preview"

Icon Generation

gemini --yolo "/icon 'minimalist app logo for productivity tool' --sizes='64,128,256,512' --type='app-icon' --corners='rounded'"

Diagram Generation

gemini --yolo "/diagram 'user authentication flow with OAuth' --type='flowchart' --style='modern'"

Output Location

All generated images are saved to ./nanobanana-output/ in the current directory.

Presenting Results

After generation completes:

• List contents of ./nanobanana-output/ to find generated files
• Present the most recent image(s) to the user
• Offer to regenerate with variations if needed

Refinements and Iterations

When the user asks for changes:

• "Try again" / "Give me options": Regenerate with --count=3
• "Make it more [adjective]": Adjust prompt and regenerate
• "Edit this one": Use gemini --yolo "/edit nanobanana-output/filename.png 'adjustment'"
• "Different style": Add --styles="requested_style" to the command

Prompt Tips

• Be specific: Include style, mood, colors, composition details
• Add "no text": If you don't want text rendered in the image
• Reference styles: "editorial photography", "flat illustration", "3D render", "watercolor"
• Specify aspect ratio context: "wide banner", "square thumbnail", "vertical story"

Troubleshooting

| Problem | Solution |

|---------|----------|

| GEMINI_API_KEY not set | export GEMINI_API_KEY="your-key" |

| Extension not found | Run install command from setup section |

| Quota exceeded | Wait for reset or switch to flash model |

| Image generation failed | Check prompt for policy violations, simplify request |

| Output directory missing | Will be created automatically on first run |