Pollinations Multimodal MCP Server

Instructions

Implementation Reference

• src/services/imageService.js:84-131 (handler)

  The primary handler function for the 'generateImage' MCP tool. Validates input parameters, generates an image URL internally, fetches the image, converts it to base64-encoded data, and constructs an MCP response with image content and metadata.

  async function generateImage(params) {
      const { prompt, options = {} } = params;
  
      if (!prompt || typeof prompt !== "string") {
          throw new Error("Prompt is required and must be a string");
      }
  
      // First, generate the image URL (but don't use the MCP response format)
      const urlResult = await _generateImageUrlInternal(prompt, options);
  
      try {
          // Fetch the image from the URL
          const response = await fetch(urlResult.imageUrl);
  
          if (!response.ok) {
              throw new Error(`Failed to generate image: ${response.statusText}`);
          }
  
          // Get the image data as an ArrayBuffer
          const imageBuffer = await response.arrayBuffer();
  
          // Convert the ArrayBuffer to a base64 string
          const base64Data = Buffer.from(imageBuffer).toString("base64");
  
          // Determine the mime type from the response headers or default to image/jpeg
          const contentType =
              response.headers.get("content-type") || "image/jpeg";
  
          const metadata = {
              prompt: urlResult.prompt,
              width: urlResult.width,
              height: urlResult.height,
              model: urlResult.model,
              seed: urlResult.seed,
          };
  
          // Return the response in MCP format
          return createMCPResponse([
              createImageContent(base64Data, contentType),
              createTextContent(
                  `Generated image from prompt: "${prompt}"\n\nImage metadata: ${JSON.stringify(metadata, null, 2)}`,
              ),
          ]);
      } catch (error) {
          console.error("Error generating image:", error);
          throw error;
      }
  }

• src/services/imageService.js:197-222 (schema)

  Zod input schema for the 'generateImage' tool defining required 'prompt' string and optional 'options' object with model, seed, width, and height parameters.

  {
      prompt: z
          .string()
          .describe("The text description of the image to generate"),
      options: z
          .object({
              model: z
                  .string()
                  .optional()
                  .describe("Model name to use for generation"),
              seed: z
                  .number()
                  .optional()
                  .describe("Seed for reproducible results"),
              width: z
                  .number()
                  .optional()
                  .describe("Width of the generated image"),
              height: z
                  .number()
                  .optional()
                  .describe("Height of the generated image"),
          })
          .optional()
          .describe("Additional options for image generation"),
  },

• src/services/imageService.js:194-224 (registration)

  Tool registration array for 'generateImage' containing name, description, input schema, and handler reference. Exported as part of imageTools for use in the main server.

  [
      "generateImage",
      "Generate an image and return the base64-encoded data",
      {
          prompt: z
              .string()
              .describe("The text description of the image to generate"),
          options: z
              .object({
                  model: z
                      .string()
                      .optional()
                      .describe("Model name to use for generation"),
                  seed: z
                      .number()
                      .optional()
                      .describe("Seed for reproducible results"),
                  width: z
                      .number()
                      .optional()
                      .describe("Width of the generated image"),
                  height: z
                      .number()
                      .optional()
                      .describe("Height of the generated image"),
              })
              .optional()
              .describe("Additional options for image generation"),
      },
      generateImage,
  ],

• src/services/imageService.js:25-44 (helper)

  Internal utility function that builds the Pollinations image API URL from prompt and options, used by both generateImage and generateImageUrl handlers.

  async function _generateImageUrlInternal(prompt, options = {}) {
      const { model, seed, width = 1024, height = 1024 } = options;
  
      // Construct the URL with query parameters
      const encodedPrompt = encodeURIComponent(prompt);
      const path = `prompt/${encodedPrompt}`;
      const queryParams = { model, seed, width, height };
  
      const url = buildUrl(IMAGE_API_BASE_URL, path, queryParams);
  
      // Return the URL with metadata
      return {
          imageUrl: url,
          prompt,
          width,
          height,
          model,
          seed,
      };
  }

• src/index.js:87-87 (registration)

  Final MCP server registration loop that applies all tool definitions, including the 'generateImage' tool from imageTools, using McpServer.tool(name, description, schema, handler).

  toolDefinitions.forEach((tool) => server.tool(...tool));