构建笔记 MCP 服务器

本指南将介绍如何从零构建完整的 MCP（Model Context Protocol）服务器。该服务器用于管理一组 Markdown 笔记，并提供以下功能：

1. 列出并读取笔记：允许客户端浏览和查看服务器上存储的 Markdown 文件
2. 写入笔记：提供用于创建或更新笔记的 Tool
3. 提供智能提示词：生成上下文相关的提示词，例如创建每日笔记模板或总结现有内容

前提条件

• 已安装 Node.js v22.13.0 或更高版本
• 受支持的模型 Provider所提供的 API 密钥
• 现有 Mastra 项目（按照安装指南设置新项目）

添加必要的依赖项和文件

创建 MCP 服务器之前，需要先安装其他依赖项并设置样板文件夹结构。

1. 将 @mastra/mcp 添加到项目：

   npm

   npm install @mastra/mcp@latest

   pnpm

   pnpm add @mastra/mcp@latest

   Yarn

   yarn add @mastra/mcp@latest

   Bun

   bun add @mastra/mcp@latest

2. 按照默认安装指南操作后，项目中会包含与本指南无关的文件。可以安全地将其删除：

   rm -rf src/mastra/agents src/mastra/workflows src/mastra/tools/weather-tool.ts

   还应按如下方式修改 src/mastra/index.ts 文件：

   src/mastra/index.ts

   import { Mastra } from '@mastra/core'
   import { PinoLogger } from '@mastra/loggers'
   import { LibSQLStore } from '@mastra/libsql'
   
   export const mastra = new Mastra({
     storage: new LibSQLStore({
       id: 'mastra-storage',
       // stores telemetry, evals, ... into memory storage, if it needs to persist, change to file:../mastra.db
       url: ':memory:',
     }),
     logger: new PinoLogger({
       name: 'Mastra',
       level: 'info',
     }),
   })

3. 为 MCP 服务器逻辑创建专用目录，并为笔记创建 notes 目录：

   mkdir notes src/mastra/mcp

   创建以下文件：

   touch src/mastra/mcp/{server,resources,prompts}.ts

   • server.ts：包含 MCP 服务器的主要配置
   • resources.ts：处理笔记文件的列出和读取
   • prompts.ts：包含智能提示词的逻辑

   最终目录结构应如下所示：

   <your-project-name>/
   ├── notes/
   └── src/
       └── mastra/
           ├── index.ts
           ├── mcp/
           │   ├── server.ts
           │   ├── resources.ts
           │   └── prompts.ts
           └── tools/

创建 MCP 服务器

下面添加 MCP 服务器。

1. 在 src/mastra/mcp/server.ts 中定义 MCP 服务器实例：

   src/mastra/mcp/server.ts

   import { MCPServer } from '@mastra/mcp'
   
   export const notes = new MCPServer({
     id: 'notes',
     name: 'Notes Server',
     version: '0.1.0',
     tools: {},
   })

   在 src/mastra/index.ts 的 Mastra 实例中注册此 MCP 服务器。notes key 是 MCP 服务器的公开标识符：

   src/mastra/index.ts

   import { Mastra } from '@mastra/core'
   import { PinoLogger } from '@mastra/loggers'
   import { LibSQLStore } from '@mastra/libsql'
   import { notes } from './mcp/server'
   
   export const mastra = new Mastra({
     storage: new LibSQLStore({
       id: 'mastra-storage',
       // stores telemetry, evals, ... into memory storage, if it needs to persist, change to file:../mastra.db
       url: ':memory:',
     }),
     logger: new PinoLogger({
       name: 'Mastra',
       level: 'info',
     }),
     mcpServers: {
       notes,
     },
   })

2. Resource handler 允许客户端发现并读取服务器管理的内容。实现用于处理 notes 目录中 Markdown 文件的 handler。将以下内容添加到 src/mastra/mcp/resources.ts 文件：

   src/mastra/mcp/resources.ts

   import fs from 'fs/promises'
   import path from 'path'
   import { fileURLToPath } from 'url'
   import type { MCPServerResources, Resource } from '@mastra/mcp'
   
   const __filename = fileURLToPath(import.meta.url)
   const __dirname = path.dirname(__filename)
   const NOTES_DIR = path.resolve(__dirname, '../../notes') // relative to the default output directory
   
   const listNoteFiles = async (): Promise<Resource[]> => {
     try {
       await fs.mkdir(NOTES_DIR, { recursive: true })
       const files = await fs.readdir(NOTES_DIR)
       return files
         .filter(file => file.endsWith('.md'))
         .map(file => {
           const title = file.replace('.md', '')
           return {
             uri: `notes://${title}`,
             name: title,
             description: `A note about ${title}`,
             mime_type: 'text/markdown',
           }
         })
     } catch (error) {
       console.error('Error listing note resources:', error)
       return []
     }
   }
   
   const readNoteFile = async (uri: string): Promise<string | null> => {
     const title = uri.replace('notes://', '')
     const notePath = path.join(NOTES_DIR, `${title}.md`)
     try {
       return await fs.readFile(notePath, 'utf-8')
     } catch (error) {
       if ((error as NodeJS.ErrnoException).code !== 'ENOENT') {
         console.error(`Error reading resource ${uri}:`, error)
       }
       return null
     }
   }
   
   export const resourceHandlers: MCPServerResources = {
     listResources: listNoteFiles,
     getResourceContent: async ({ uri }: { uri: string }) => {
       const content = await readNoteFile(uri)
       if (content === null) return { text: '' }
       return { text: content }
     },
   }

   在 src/mastra/mcp/server.ts 中注册这些 resource handler：

   src/mastra/mcp/server.ts

   import { MCPServer } from '@mastra/mcp'
   import { resourceHandlers } from './resources'
   
   export const notes = new MCPServer({
     id: 'notes',
     name: 'Notes Server',
     version: '0.1.0',
     tools: {},
     resources: resourceHandlers,
   })

3. Tool 是服务器可以执行的操作。下面创建一个 write Tool。 首先，在 src/mastra/tools/write-note.ts 中定义该 Tool：

   src/mastra/tools/write-note.ts

   import { createTool } from '@mastra/core/tools'
   import { z } from 'zod'
   import { fileURLToPath } from 'url'
   import path from 'node:path'
   import fs from 'fs/promises'
   
   const __filename = fileURLToPath(import.meta.url)
   const __dirname = path.dirname(__filename)
   const NOTES_DIR = path.resolve(__dirname, '../../../notes')
   
   export const writeNoteTool = createTool({
     id: 'write',
     description: 'Write a new note or overwrite an existing one.',
     inputSchema: z.object({
       title: z.string().nonempty().describe('The title of the note. This will be the filename.'),
       content: z.string().nonempty().describe('The markdown content of the note.'),
     }),
     outputSchema: z.string().nonempty(),
     execute: async inputData => {
       try {
         const { title, content } = inputData
         const filePath = path.join(NOTES_DIR, `${title}.md`)
         await fs.mkdir(NOTES_DIR, { recursive: true })
         await fs.writeFile(filePath, content, 'utf-8')
         return `Successfully wrote to note \"${title}\".`
       } catch (error: any) {
         return `Error writing note: ${error.message}`
       }
     },
   })

   在 src/mastra/mcp/server.ts 中注册此 Tool：

   src/mastra/mcp/server.ts

   import { MCPServer } from '@mastra/mcp'
   import { resourceHandlers } from './resources'
   import { writeNoteTool } from '../tools/write-note'
   
   export const notes = new MCPServer({
     id: 'notes',
     name: 'Notes Server',
     version: '0.1.0',
     resources: resourceHandlers,
     tools: {
       write: writeNoteTool,
     },
   })

4. Prompt handler 为客户端提供可直接使用的提示词。你将添加以下三个提示词：

   • 每日笔记
   • 总结笔记
   • 集思广益

   这需要安装几个 Markdown 解析库：

   npm install unified remark-parse gray-matter @types/unist

   在 src/mastra/mcp/prompts.ts 中实现提示词：

   src/mastra/mcp/prompts.ts

   import type { MCPServerPrompts } from '@mastra/mcp'
   import { unified } from 'unified'
   import remarkParse from 'remark-parse'
   import matter from 'gray-matter'
   import type { Node } from 'unist'
   
   const prompts = [
     {
       name: 'new_daily_note',
       description: 'Create a new daily note.',
       version: '1.0.0',
     },
     {
       name: 'summarize_note',
       description: 'Give me a TL;DR of the note.',
       version: '1.0.0',
     },
     {
       name: 'brainstorm_ideas',
       description: 'Brainstorm new ideas based on a note.',
       version: '1.0.0',
     },
   ]
   
   function stringifyNode(node: Node): string {
     if ('value' in node && typeof node.value === 'string') return node.value
     if ('children' in node && Array.isArray(node.children))
       return node.children.map(stringifyNode).join('')
     return ''
   }
   
   export async function analyzeMarkdown(md: string) {
     const { content } = matter(md)
     const tree = unified().use(remarkParse).parse(content)
     const headings: string[] = []
     const wordCounts: Record<string, number> = {}
     let currentHeading = 'untitled'
     wordCounts[currentHeading] = 0
     tree.children.forEach(node => {
       if (node.type === 'heading' && node.depth === 2) {
         currentHeading = stringifyNode(node)
         headings.push(currentHeading)
         wordCounts[currentHeading] = 0
       } else {
         const textContent = stringifyNode(node)
         if (textContent.trim()) {
           wordCounts[currentHeading] =
             (wordCounts[currentHeading] || 0) + textContent.split(/\\s+/).length
         }
       }
     })
     return { headings, wordCounts }
   }
   
   const getPromptMessages: MCPServerPrompts['getPromptMessages'] = async ({ name, args }) => {
     switch (name) {
       case 'new_daily_note':
         const today = new Date().toISOString().split('T')[0]
         return [
           {
             role: 'user',
             content: {
               type: 'text',
               text: `Create a new note titled \"${today}\" with sections: \"## Tasks\", \"## Meetings\", \"## Notes\".`,
             },
           },
         ]
       case 'summarize_note':
         if (!args?.noteContent) throw new Error('No content provided')
         const metaSum = await analyzeMarkdown(args.noteContent as string)
         return [
           {
             role: 'user',
             content: {
               type: 'text',
               text: `Summarize each section in ≤ 3 bullets.\\n\\n### Outline\\n${metaSum.headings.map(h => `- ${h} (${metaSum.wordCounts[h] || 0} words)`).join('\\n')}`.trim(),
             },
           },
         ]
       case 'brainstorm_ideas':
         if (!args?.noteContent) throw new Error('No content provided')
         const metaBrain = await analyzeMarkdown(args.noteContent as string)
         return [
           {
             role: 'user',
             content: {
               type: 'text',
               text: `Brainstorm 3 ideas for underdeveloped sections below ${args?.topic ? `on ${args.topic}` : '.'}\\n\\nUnderdeveloped sections:\\n${metaBrain.headings.length ? metaBrain.headings.map(h => `- ${h}`).join('\\n') : '- (none, pick any)'}`,
             },
           },
         ]
       default:
         throw new Error(`Prompt \"${name}\" not found`)
     }
   }
   
   export const promptHandlers: MCPServerPrompts = {
     listPrompts: async () => prompts,
     getPromptMessages,
   }

   在 src/mastra/mcp/server.ts 中注册这些 prompt handler：

   src/mastra/mcp/server.ts

   import { MCPServer } from '@mastra/mcp'
   import { resourceHandlers } from './resources'
   import { writeNoteTool } from '../tools/write-note'
   import { promptHandlers } from './prompts'
   
   export const notes = new MCPServer({
     id: 'notes',
     name: 'Notes Server',
     version: '0.1.0',
     resources: resourceHandlers,
     prompts: promptHandlers,
     tools: {
       write: writeNoteTool,
     },
   })

运行服务器

你已经创建了第一个 MCP 服务器！现在可以启动 Mastra 开发服务器并打开 Studio 进行尝试：

npm run dev

在浏览器中打开 http://localhost:4111。在左侧边栏中选择 MCP Servers，然后选择 notes MCP 服务器。

现在会显示如何将 MCP 服务器添加到 IDE 的说明。你可以将此 MCP 服务器与任何 MCP Client 配合使用。还可以在右侧的 Available Tools 下选择 write Tool。

在 write Tool 中进行尝试：名称输入 test，Markdown 内容输入 this is a test。选择 Submit 后，notes 中会出现新的 test.md 文件。