json-mcp-server

#!/usr/bin/env node import { Server } from '@modelcontextprotocol/sdk/server/index.js' import { StdioServerTransport } from '@modelcontextprotocol/sdk/server/stdio.js' import { CallToolRequestSchema, ListToolsRequestSchema, ToolSchema, } from '@modelcontextprotocol/sdk/types.js' import { z } from 'zod' import { readFileSync } from 'fs' import { zodToJsonSchema } from 'zod-to-json-schema' import fs from 'fs' import _path from 'path' import os from 'os' const ToolInputSchema = ToolSchema.shape.inputSchema type ToolInput = z.infer<typeof ToolInputSchema> const packageJson = JSON.parse( readFileSync(new URL('../package.json', import.meta.url), 'utf-8') ) const SERVER_VERSION = packageJson.version // Server setup const server = new Server( { name: 'json-mcp-server', version: SERVER_VERSION, }, { capabilities: { tools: {}, }, } ) // Schema definitions const PathArgSchema = z.object({ path: z.string(), }) const SplitArgSchema = z.object({ path: z.string(), numObjects: z.number().int().positive(), }) // Function implementation const expandHome = (filepath: string) => { if (filepath.startsWith('~/') || filepath === '~') { return _path.join(os.homedir(), filepath.slice(1)) } return filepath } const validatePath = async (requestedPath: string): Promise<string> => { const expandedPath = expandHome(requestedPath) const absolute = _path.isAbsolute(expandedPath) ? _path.resolve(expandedPath) : _path.resolve(process.cwd(), expandedPath) try { const realPath = await fs.promises.realpath(absolute) return realPath } catch (error) { const parentDir = _path.dirname(absolute) try { return absolute } catch { throw new Error(`Parent directory does not exist: ${parentDir}`) } } } const getParentDir = async (requestedPath: string): Promise<string> => { const expandedPath = expandHome(requestedPath) const absolute = _path.isAbsolute(expandedPath) ? _path.resolve(expandedPath) : _path.resolve(process.cwd(), expandedPath) try { const parentDir = _path.dirname(absolute) return parentDir } catch (error) { throw new Error('Parent directory does not exist') } } export const getAllFileNames = async ( dir: string, extension: string ): Promise<string[]> => { try { const filenames = await fs.promises.readdir(dir) return filenames.filter((fn: string) => fn.endsWith(extension)) } catch (error) { throw new Error(`No such folder ${dir}`) } } const getAllJsonNames = async (dir: string): Promise<string[]> => getAllFileNames(dir, '.json') const getMultipleJsonFilePath = async (fileDir: string): Promise<string[]> => { const filePaths: string[] = [] const fileNames = await getAllJsonNames(fileDir) for (let index = 0; index < fileNames.length; index++) { filePaths.push(`${fileDir}/${fileNames[index]}`) } return filePaths } const readFileToJson = async (fileName: string): Promise<any[]> => { try { const content = await fs.promises.readFile(fileName, 'utf-8') return JSON.parse(content) } catch (error) { throw new Error(`Error reading or parsing file ${fileName}: ${error}`) } } const parseMultipleJson = async (fileDir: string) => { const multipleJson: any = [] const fileNames = await getMultipleJsonFilePath(fileDir) for (let index = 0; index < fileNames.length; index++) { multipleJson.push(readFileToJson(fileNames[index])) } return multipleJson } const loadFlatJsons = async (path: string) => { const promises = await parseMultipleJson(path) if (promises.length === 0) throw new Error(`No files in ${path}`) const jsons = await Promise.all(promises) return jsons.flat() } // Tool handlers server.setRequestHandler(ListToolsRequestSchema, async () => { return { tools: [ { name: 'split', description: 'Split a JSON file into a specified number of objects', inputSchema: zodToJsonSchema(SplitArgSchema) as ToolInput, }, { name: 'merge', description: 'Merge JSON files into a one JSON file', inputSchema: zodToJsonSchema(PathArgSchema) as ToolInput, }, ], } }) server.setRequestHandler(CallToolRequestSchema, async (request) => { try { const { name, arguments: args } = request.params switch (name) { case 'split': { const parsed = SplitArgSchema.safeParse(args) if (!parsed.success) { throw new Error(`Invalid arguments for split: ${parsed.error}`) } const { path, numObjects } = parsed.data const validPath = await validatePath(path) const content = await fs.promises.readFile(validPath, 'utf-8') const folder = await getParentDir(path) const jsonData = JSON.parse(content) if (numObjects >= jsonData.length / 2) { throw new Error( `The number of objects (${numObjects}) per file cannot be half or more of the total (${jsonData.length}) JSON data length.` ) } const totalParts = Math.ceil(jsonData.length / numObjects) await Promise.all( Array.from({ length: totalParts }, async (_, i) => { const partArray = jsonData .slice(i * numObjects, (i + 1) * numObjects) ?.flat() const partFileName = _path.join(folder, `part${i + 1}.json`) try { await fs.promises.writeFile( partFileName, JSON.stringify(partArray, null, 2) ) console.log(`Successfully wrote ${partFileName}`) } catch (err) { console.error(`Error writing file ${partFileName}:`, err) } }) ) return { content: [ { type: 'text', text: `Successfully splitted to ${parsed.data.path}`, }, ], } } case 'merge': { const parsed = PathArgSchema.safeParse(args) if (!parsed.success) { throw new Error(`Invalid arguments for merge: ${parsed.error}`) } const { path } = parsed.data const validPath = await validatePath(path) const content = await loadFlatJsons(validPath) const fileName = _path.join(validPath, 'merged.json') try { await fs.promises.writeFile( fileName, JSON.stringify(content, null, 2) ) console.log(`Successfully wrote ${fileName}`) } catch (err) { console.error(`Error writing file ${fileName}:`, err) } return { content: [ { type: 'text', text: `Successfully merged to ${fileName}`, }, ], } } default: throw new Error(`Unknown tool: ${name}`) } } catch (error) { const errorMessage = error instanceof Error ? error.message : String(error) return { content: [{ type: 'text', text: `Error: ${errorMessage}` }], isError: true, } } }) // Start server export async function main() { try { const transport = new StdioServerTransport() await server.connect(transport) console.error(`JSON MCP Server ${SERVER_VERSION} running on stdio`) } catch (error) { console.error('Error during startup:', error) process.exit(1) } } main().catch((error) => { console.error('Fatal error in main():', error) process.exit(1) })