image-gen

name

image-gen

description

Generate images via the Gemini MCP server (Imagen 4 family and Nano Banana family). Use this skill whenever the user wants to create, generate, design, or produce any image, illustration, icon, logo, hero, banner, mockup, diagram, screenshot stand-in, social card, poster, or other visual asset — even when they don't name a model and even when they phrase it casually ("I need an icon here", "make me a header image", "generate a thumbnail"). Use it for editing or iterating on previously generated images too. The skill picks the right model for the task, crafts a strong prompt, and saves the image into the project.

image-gen

Generate images from inside Claude Code using the Gemini MCP server. This skill exists because picking the right model and writing a strong prompt are the two things that most determine output quality, and both benefit from codified conventions rather than ad-hoc decisions every time.

When this skill applies

Any request that ends in a generated visual asset. Common phrasings:

• "Generate an icon for…"
• "I need a hero image for the landing page"
• "Make me a placeholder for the user avatar"
• "Create a diagram showing X"
• "Design a logo for…"
• "Give me a poster / banner / social card / thumbnail"
• "Generate three variations of…"
• "Edit this image to…" (when a previously generated image is in context)

If the user references an image they want and there's no upload, default to generating it.

Prerequisites

The gemini MCP server must be installed and configured with GEMINI_API_KEY. If the tools aren't available, tell the user to install it:

claude mcp add gemini -s user -- env GEMINI_API_KEY=YOUR_KEY npx -y @rlabs-inc/gemini-mcp

…then restart Claude Code. Don't proceed with the skill until the MCP tools appear.

The workflow

Every image-generation request goes through the same four steps. Don't skip steps; even fast requests benefit from the 10 seconds of thinking.

Step 1 — Clarify intent (silently, in your head)

Before reaching for a tool, answer these questions from the conversation context. Don't ask the user unless something is genuinely ambiguous — guess and state your assumptions inline if needed.

• What is the asset for? (hero, icon, diagram, social, poster, mockup, decorative)
• Where will it live? (web header → 16:9, app icon → 1:1, mobile splash → 9:16, print poster → 3:4)
• What's the aesthetic? (photorealistic, illustrated, flat/geometric, 3D, sketch, retro)
• Is there text in the image? (changes model choice significantly)
• Does it need to match existing assets? (reference style/colors from earlier in the conversation)

Step 2 — Pick the model

Use the table in references/model-selection.md for the full decision tree. Quick version:

If the task is…	Use
Photorealistic, product shot, high realism	imagen-4.0-ultra-generate-001
Bulk drafts, social tiles, low cost	imagen-4.0-fast-generate-001
General quality images	imagen-4.0-generate-001
Has legible text in the image (poster, banner with copy, infographic)	Nano Banana 2 (gemini-3.1-flash-image-preview)
Editing or iterating with reference images	Nano Banana 2
Complex reasoning-heavy prompts, diagrams, 4K	Nano Banana Pro (gemini-3-pro-image-preview)
User didn't specify and budget unclear	imagen-4.0-generate-001 (sensible default)

Read references/model-selection.md for the full decision tree and rationale when the task is non-obvious.

Step 3 — Craft the prompt

This is where most quality comes from. Read references/prompt-craft.md for the full conventions; the short version:

Build prompts in this order: subject → context → style → quality modifiers.

A sketch (style) of a modern apartment building (subject) surrounded by skyscrapers (context). Quality: detailed, professional.

For photorealism, include camera/lens cues from the photography table (e.g. "35mm portrait, golden hour, shallow depth of field"). For text-in-image, keep the text under 25 characters and specify font feel (e.g. "bold serif", "hand-drawn"). For illustrations, name the medium ("charcoal drawing", "art deco poster", "pastel painting"). For style consistency across multiple images in one session, lock a "style anchor" phrase and reuse it verbatim.

Always do a mental pass: would this prompt give a sharp, specific image, or a generic one? If generic, add details until specific.

Step 4 — Generate and present

Call the MCP tool. Default to 1 image unless the user asked for variations or batch — image generation is not free.

State briefly what you did (model + key choices), then show the result. If the file path is returned, surface it so they can open it. Don't post-mortem the prompt unless asked.

If the first result isn't right:

1. Diagnose what specifically is off (composition, lighting, subject, style)
2. Adjust only the relevant part of the prompt, not the whole thing
3. Use the same seed if you want to vary one dimension; new seed if you want a different draw

Output handling

By default the MCP server writes images to the current working directory (or GEMINI_OUTPUT_DIR if set). For project-scoped work, suggest a path like assets/generated/ or public/images/ based on the project structure visible in context. If the project has a .gitignore, mention whether the generated dir is ignored.

Filename convention from the server is already sensible ({model}_{timestamp}_{prompt-slug}.png); don't try to rename unless asked.

Cost awareness

Indicative pricing as of 2026:

• Imagen 4 Fast: ~$0.02/image
• Imagen 4: ~$0.04/image
• Imagen 4 Ultra: ~$0.06/image
• Nano Banana 2: cheaper Flash-tier pricing
• Nano Banana Pro: ~$0.13/image (most expensive, save for final renders)

For drafts and exploration, prefer Fast or Nano Banana 2. Reserve Ultra / Pro for the final pick.

Common patterns

Generating a set of UI assets

When the user wants multiple coordinated assets (e.g. "make me icons for these three features"), lock the style upfront in a single style anchor string and reuse it across each generation. Run them sequentially so you can adjust the anchor if the first feels off.

Iterating on a single image

Use seed for reproducibility. Generate once, get a seed in the result, then re-prompt with the same seed plus the targeted edit. Switch to Nano Banana 2 for any edit that requires a reference to the previous output.

Diagrams and architecture sketches

Use Nano Banana Pro — its reasoning improves spatial layout. Describe the structure ("three boxes labeled A, B, C connected by arrows showing data flow from A through B to C, isometric perspective, line-art style with subtle color fills").

Working in a project context

If the user is working on a React/web project (look at recent file context), bias toward web-relevant aspect ratios (16:9 hero, 1:1 social, 9:16 mobile, 4:5 product card) and suggest saving to a path that matches the project's existing asset structure.

Anti-patterns

• Don't generate before clarifying aspect ratio if it matters for the use case. A 1:1 logo and a 16:9 hero need different generations.
• Don't use Nano Banana Pro for casual exploration — it's the most expensive option.
• Don't stack ten quality modifiers ("4K HDR cinematic professional ultra-detailed masterpiece") — Imagen and Nano Banana respond better to specific descriptors than to a pile of buzzwords.
• Don't explain the prompt engineering after generation unless the user asks. Show the image and move on.
• Don't silently regenerate if the first image is "close" — ask whether to iterate or accept.

Dexterlabs project context

When generating images for this project, always read wiki/expertise/image-workflow.md first. Key rules:

• Published content images (notes, products, mailings, projects) → save to content/{type}/{slug}/, then run pnpm optimize. Reference the .webp filename in frontmatter.
• Dexterlabs cartoon style → use the character sheet + environment compositor workflow documented in wiki/expertise/artwork-prompts.md. Character sheets live in content/art/characters/, environment plates in content/art/environments/. Use gemini-3-pro-image-preview (supports reference images).
• Art library (content/art/) → not optimized, not published directly. Working assets only.

References

• references/model-selection.md — full decision tree for choosing models with examples
• references/prompt-craft.md — prompt construction conventions, photography cues, style references, text-in-image rules
• wiki/expertise/image-workflow.md — where to save images and how to run optimize
• wiki/expertise/artwork-prompts.md — Dexterlabs cartoon style, character sheets, environment plates, scene compositor workflow