PubChem MCP Server

/** * @fileoverview Defines the core logic, schemas, and types for the `pubchem_get_compound_image` tool. * This tool fetches the raw image data for a given compound. * @module src/mcp-server/tools/getCompoundImageUrl/logic */ import { z } from "zod"; import { pubChemApiClient } from "../../../services/pubchem/pubchemApiClient.js"; import { BaseErrorCode, McpError } from "../../../types-global/errors.js"; import { logger, type RequestContext } from "../../../utils/index.js"; // 1. Define and export the Zod schema for input validation export const PubchemGetCompoundImageInputSchema = z.object({ cid: z .number() .int() .positive() .describe( "The PubChem Compound ID (CID) for which to fetch the image. Must be a positive integer.", ), size: z .enum(["small", "large"]) .optional() .default("large") .describe( "Specifies the desired image size: 'small' (100x100) or 'large' (300x300). Defaults to 'large'.", ), }); // 2. Define and export the TypeScript type for the input export type PubchemGetCompoundImageInput = z.infer< typeof PubchemGetCompoundImageInputSchema >; // 3. Define and export the Zod schema for the tool's output export const PubchemGetCompoundImageOutputSchema = z.object({ cid: z .number() .int() .describe("The CID of the compound depicted in the image."), blob: z.instanceof(Buffer).describe("The raw image data as a Buffer object."), mimeType: z .string() .describe("The MIME type of the image (e.g., 'image/png')."), }); // 4. Define and export the TypeScript type for the output export type PubchemGetCompoundImageOutput = z.infer< typeof PubchemGetCompoundImageOutputSchema >; const PUBCHEM_IMAGE_BASE_URL = "https://pubchem.ncbi.nlm.nih.gov/rest/pug"; /** * Core logic for the `pubchem_get_compound_image` tool. It constructs the image URL, * fetches the image data, and returns it as a blob. * * @param {PubchemGetCompoundImageInput} params - The validated input parameters. * @param {RequestContext} context - The request context for logging and tracing. * @returns {Promise<PubchemGetCompoundImageOutput>} A promise that resolves with the image blob and metadata. * @throws {McpError} Throws a structured error if the image fetch fails or the CID is invalid. */ export async function pubchemGetCompoundImageLogic( params: PubchemGetCompoundImageInput, context: RequestContext, ): Promise<PubchemGetCompoundImageOutput> { logger.debug("Processing pubchem_get_compound_image logic...", { ...context, params, }); const { cid, size } = params; const imageUrl = `${PUBCHEM_IMAGE_BASE_URL}/compound/cid/${cid}/PNG?record_type=2d&image_size=${size}`; try { const arrayBuffer = await pubChemApiClient.getBlob(imageUrl, context); const result: PubchemGetCompoundImageOutput = { cid, blob: Buffer.from(arrayBuffer), mimeType: "image/png", }; logger.info(`Successfully fetched image for CID ${cid}.`, context); return result; } catch (error) { logger.error(`Failed to fetch image for CID ${cid} from ${imageUrl}`, { ...context, error, }); throw new McpError( BaseErrorCode.EXTERNAL_SERVICE_ERROR, `Failed to fetch image for CID ${cid}. The compound may not exist or there was a network issue.`, { ...context, cid, imageUrl }, ); } }