edit_image_multi
Edit or compose images using multiple reference images (up to 14) with customizable aspect ratios and resolutions.
Instructions
Edit or compose images using multiple reference images (up to 14). Uses gemini-3-pro-image-preview (Nano Banana Pro).
Input Schema
TableJSON Schema
| Name | Required | Description | Default |
|---|---|---|---|
| prompt | Yes | Description of the desired output | |
| images | Yes | Array of reference images (1-14) | |
| aspectRatio | No | Aspect ratio of the output image | 1:1 |
| imageSize | No | Output image resolution | 1K |
Implementation Reference
- src/tools/edit-image.ts:67-129 (handler)The complete implementation of edit_image_multi tool including registration, schema definition, and handler logic. This function registers the tool with the MCP server and handles multi-reference image editing by processing a prompt and up to 14 base64-encoded images through the gemini-3-pro-image-preview model.export function registerMulti(server: McpServer, ai: GoogleGenAI): void { server.registerTool( 'edit_image_multi', { title: 'Edit Image (Multi-Reference)', description: 'Edit or compose images using multiple reference images (up to 14). Uses gemini-3-pro-image-preview (Nano Banana Pro).', inputSchema: { prompt: z.string().min(1).describe('Description of the desired output'), images: z.array(z.object({ data: z.string().min(1).describe('Base64-encoded image'), mimeType: z.enum(['image/png', 'image/jpeg', 'image/webp']).default('image/png'), })).min(1).max(14).describe('Array of reference images (1-14)'), aspectRatio: AspectRatio.default('1:1').describe('Aspect ratio of the output image'), imageSize: ImageSize.default('1K').describe('Output image resolution'), }, annotations: { readOnlyHint: true, destructiveHint: false, openWorldHint: true, }, }, async ({ prompt, images, aspectRatio, imageSize }) => { try { const parts = [ { text: prompt }, ...images.map((img: { mimeType: string; data: string }) => ({ inlineData: { mimeType: img.mimeType, data: img.data }, })), ]; const response = await ai.models.generateContent({ model: 'gemini-3-pro-image-preview', contents: parts, config: { responseModalities: ['TEXT', 'IMAGE'], imageConfig: { aspectRatio, imageSize }, }, }); const result = extractImageFromResponse(response); if (!result) { return { content: [{ type: 'text' as const, text: 'No image was produced. Try a different prompt.' }], isError: true, }; } if (!validateImageSize(result.data)) { return { content: [{ type: 'text' as const, text: 'Output image exceeds size limit. Try a smaller imageSize.' }], isError: true, }; } return { content: [{ type: 'image' as const, data: result.data, mimeType: result.mimeType }], }; } catch (error) { return formatToolError(error); } }, ); }
- src/index.ts:9-31 (registration)Tool registration in the main server file. Imports registerMulti as registerEditImageMulti and registers it with the MCP server instance.import { register as registerEditImage, registerMulti as registerEditImageMulti } from './tools/edit-image.js'; const GEMINI_API_KEY = process.env.GEMINI_API_KEY; if (!GEMINI_API_KEY) { console.error('GEMINI_API_KEY environment variable is required'); process.exit(1); } const ai = createClient(GEMINI_API_KEY); const server = new McpServer( { name: 'gemini', version: '2.0.0' }, { capabilities: { logging: {} } }, ); // Register all 7 tools registerGenerateText(server, ai); registerChat(server, ai); registerGenerateWithSearch(server, ai); registerCodeExecution(server, ai); registerGenerateImage(server, ai); registerEditImage(server, ai); registerEditImageMulti(server, ai);
- src/types.ts:18-24 (schema)Type definitions for schema validation used by edit_image_multi tool, defining allowed aspect ratios and image sizes.export const AspectRatio = z.enum([ '1:1', '2:3', '3:2', '3:4', '4:3', '4:5', '5:4', '9:16', '16:9', '21:9', ]); export type AspectRatio = z.infer<typeof AspectRatio>; export const ImageSize = z.enum(['1K', '2K', '4K']); export type ImageSize = z.infer<typeof ImageSize>;
- src/utils/image.ts:1-20 (helper)Helper utilities used by edit_image_multi handler: validateImageSize checks if base64 image size is within 2MB limit, extractImageFromResponse parses the Gemini API response to extract the generated image data.const MAX_IMAGE_SIZE = 2 * 1024 * 1024; // 2MB — conservative limit for MCP stdio transport export function validateImageSize(base64: string): boolean { const sizeInBytes = Math.ceil(base64.length * 3 / 4); return sizeInBytes <= MAX_IMAGE_SIZE; } export function extractImageFromResponse(response: any): { data: string; mimeType: string } | null { const parts = response?.candidates?.[0]?.content?.parts; if (!parts) return null; for (const part of parts) { if (part.inlineData) { return { data: part.inlineData.data, mimeType: part.inlineData.mimeType, }; } } return null; }
- src/utils/errors.ts:1-7 (helper)Error formatting utility used by edit_image_multi handler to format errors into the expected MCP tool response structure.export function formatToolError(error: unknown) { const text = error instanceof Error ? error.message : String(error); return { content: [{ type: 'text' as const, text }], isError: true, }; }