Nano Banana Pro MCP

import type { GeminiRequest, GeminiResponse, GenerateImageOptions, GeneratedImage, DescribeImageOptions, } from "./types.js"; const GEMINI_API_BASE = "https://generativelanguage.googleapis.com/v1beta/models"; // Allowed models for image generation const ALLOWED_MODELS = [ "gemini-3-pro-image-preview", // Nano Banana Pro (highest quality) "gemini-2.5-flash-preview-05-20", // Nano Banana (fast) "gemini-2.0-flash-exp", // Widely available fallback ] as const; const DEFAULT_MODEL = "gemini-3-pro-image-preview"; export class GeminiImageClient { private apiKey: string; constructor(apiKey: string) { if (!apiKey) { throw new Error("GEMINI_API_KEY is required"); } this.apiKey = apiKey; } async generateImage(options: GenerateImageOptions): Promise<GeneratedImage> { const { prompt, aspectRatio, imageSize, images } = options; const model = options.model || DEFAULT_MODEL; // Validate model against allowlist to prevent URL manipulation if (!ALLOWED_MODELS.includes(model as typeof ALLOWED_MODELS[number])) { throw new Error( `Invalid model: ${model}. Allowed: ${ALLOWED_MODELS.join(", ")}` ); } // Only certain models support imageConfig (aspect ratio, size) const supportsImageConfig = model.includes("image") || model.includes("imagen"); // Build request parts array: text prompt + optional input images const requestParts: Array<{ text: string } | { inlineData: { mimeType: string; data: string } }> = [ { text: prompt } ]; // Add input images if provided (for reference or editing) if (images && images.length > 0) { for (const img of images) { requestParts.push({ inlineData: { mimeType: img.mimeType, data: img.data, }, }); } } const requestBody: GeminiRequest = { contents: [ { parts: requestParts, }, ], generationConfig: { responseModalities: ["TEXT", "IMAGE"], ...(supportsImageConfig && (aspectRatio || imageSize) ? { imageConfig: { ...(aspectRatio && { aspectRatio }), ...(imageSize && { imageSize }), }, } : {}), }, }; const url = `${GEMINI_API_BASE}/${model}:generateContent?key=${this.apiKey}`; const response = await fetch(url, { method: "POST", headers: { "Content-Type": "application/json", }, body: JSON.stringify(requestBody), }); if (!response.ok) { const errorText = await response.text(); throw new Error(`Gemini API error (${response.status}): ${errorText}`); } const data = (await response.json()) as GeminiResponse; if (data.error) { throw new Error(`Gemini API error: ${data.error.message}`); } if (!data.candidates || data.candidates.length === 0) { throw new Error("No image generated - empty response from Gemini"); } const responseParts = data.candidates[0].content.parts; let imageData: GeneratedImage | null = null; let description: string | undefined; for (const part of responseParts) { if ("inlineData" in part && part.inlineData) { imageData = { mimeType: part.inlineData.mimeType, base64Data: part.inlineData.data, }; } else if ("text" in part && part.text) { description = part.text; } } if (!imageData) { throw new Error("No image data in Gemini response"); } return { ...imageData, description, }; } async describeImage(options: DescribeImageOptions): Promise<string> { const { images, prompt } = options; const model = options.model || DEFAULT_MODEL; // Validate model against allowlist to prevent URL manipulation if (!ALLOWED_MODELS.includes(model as typeof ALLOWED_MODELS[number])) { throw new Error( `Invalid model: ${model}. Allowed: ${ALLOWED_MODELS.join(", ")}` ); } if (!images || images.length === 0) { throw new Error("At least one image is required"); } // Build request parts: prompt + images const defaultPrompt = "Describe this image in detail. What do you see?"; const requestParts: Array<{ text: string } | { inlineData: { mimeType: string; data: string } }> = [ { text: prompt || defaultPrompt } ]; for (const img of images) { requestParts.push({ inlineData: { mimeType: img.mimeType, data: img.data, }, }); } const requestBody: GeminiRequest = { contents: [ { parts: requestParts, }, ], generationConfig: { responseModalities: ["TEXT"], // Text only, no image output }, }; const url = `${GEMINI_API_BASE}/${model}:generateContent?key=${this.apiKey}`; const response = await fetch(url, { method: "POST", headers: { "Content-Type": "application/json", }, body: JSON.stringify(requestBody), }); if (!response.ok) { const errorText = await response.text(); throw new Error(`Gemini API error (${response.status}): ${errorText}`); } const data = (await response.json()) as GeminiResponse; if (data.error) { throw new Error(`Gemini API error: ${data.error.message}`); } if (!data.candidates || data.candidates.length === 0) { throw new Error("No response from Gemini"); } const responseParts = data.candidates[0].content.parts; let description = ""; for (const part of responseParts) { if ("text" in part && part.text) { description += part.text; } } if (!description) { throw new Error("No description in Gemini response"); } return description; } }