mcp-builder

name mcp-builder description Guide for creating high-quality MCP (Model Context Protocol) servers that enable LLMs to interact with external services through well-designed tools. Use when building MCP servers to integrate external APIs or services, whether in Python (FastMCP), Node/TypeScript (MCP SDK), or C#/.NET (Microsoft MCP SDK). MCP Server Development Guide Overview Create MCP (Model Context Protocol) servers that enable LLMs to interact with external services through well-designed tools. The quality of an MCP server is measured by how well it enables LLMs to accomplish real-world tasks. Microsoft MCP Ecosystem Microsoft provides extensive MCP infrastructure for Azure and Foundry services. Understanding this ecosystem helps you decide whether to build custom servers or leverage existing ones. Server Types Type Transport Use Case Example Local stdio Desktop apps, single-user, local dev Azure MCP Server via NPM/Docker Remote Streamable HTTP Cloud services, multi-tenant, Agent Service https://mcp.ai.azure.com (Foundry) Microsoft MCP Servers Before building a custom server, check if Microsoft already provides one: Server Type Description Azure MCP Local 48+ Azure services (Storage, KeyVault, Cosmos, SQL, etc.) Foundry MCP Remote https://mcp.ai.azure.com - Models, deployments, evals, agents Fabric MCP Local Microsoft Fabric APIs, OneLake, item definitions Playwright MCP Local Browser automation and testing GitHub MCP Remote https://api.githubcopilot.com/mcp Full ecosystem: See 🔷 Microsoft MCP Patterns for complete server catalog and patterns. When to Use Microsoft vs Custom Scenario Recommendation Azure service integration Use Azure MCP Server (48 services covered) AI Foundry agents/evals Use Foundry MCP remote server Custom internal APIs Build custom server (this guide) Third-party SaaS integration Build custom server (this guide) Extending Azure MCP Follow Microsoft MCP Patterns Process 🚀 High-Level Workflow Creating a high-quality MCP server involves four main phases: Phase 1: Deep Research and Planning 1.1 Understand Modern MCP Design API Coverage vs. Workflow Tools: Balance comprehensive API endpoint coverage with specialized workflow tools. Workflow tools can be more convenient for specific tasks, while comprehensive coverage gives agents flexibility to compose operations. Performance varies by client—some clients benefit from code execution that combines basic tools, while others work better with higher-level workflows. When uncertain, prioritize comprehensive API coverage. Tool Naming and Discoverability: Clear, descriptive tool names help agents find the right tools quickly. Use consistent prefixes (e.g., github_create_issue , github_list_repos ) and action-oriented naming. Context Management: Agents benefit from concise tool descriptions and the ability to filter/paginate results. Design tools that return focused, relevant data. Some clients support code execution which can help agents filter and process data efficiently. Actionable Error Messages: Error messages should guide agents toward solutions with specific suggestions and next steps. 1.2 Study MCP Protocol Documentation Navigate the MCP specification: Start with the sitemap to find relevant pages: https://modelcontextprotocol.io/sitemap.xml Then fetch specific pages with .md suffix for markdown format (e.g., https://modelcontextprotocol.io/specification/draft.md ). Key pages to review: Specification overview and architecture Transport mechanisms (streamable HTTP, stdio) Tool, resource, and prompt definitions 1.3 Study Framework Documentation Language Selection: Language Best For SDK TypeScript (recommended) General MCP servers, broad compatibility @modelcontextprotocol/sdk Python Data/ML pipelines, FastAPI integration mcp (FastMCP) C#/.NET Azure/Microsoft ecosystem, enterprise Microsoft.Mcp.Core Transport Selection: Transport Use Case Characteristics Streamable HTTP Remote servers, multi-tenant, Agent Service Stateless, scalable, requires auth stdio Local servers, desktop apps Simple, single-user, no network Load framework documentation: MCP Best Practices : 📋 View Best Practices - Core guidelines For TypeScript (recommended): TypeScript SDK : Use WebFetch to load https://raw.githubusercontent.com/modelcontextprotocol/typescript-sdk/main/README.md ⚡ TypeScript Guide - TypeScript patterns and examples For Python: Python SDK : Use WebFetch to load https://raw.githubusercontent.com/modelcontextprotocol/python-sdk/main/README.md 🐍 Python Guide - Python patterns and examples For C#/.NET (Microsoft ecosystem): 🔷 Microsoft MCP Patterns - C# patterns, Azure MCP architecture, command hierarchy 1.4 Plan Your Implementation Understand the API: Review the service's API documentation to identify key endpoints, authentication requirements, and data models. Use web search and WebFetch as needed. Tool Selection: Prioritize comprehensive API coverage. List endpoints to implement, starting with the most common operations. Phase 2: Implementation 2.1 Set Up Project Structure See language-specific guides for project setup: ⚡ TypeScript Guide - Project structure, package.json, tsconfig.json 🐍 Python Guide - Module organization, dependencies 🔷 Microsoft MCP Patterns - C# project structure, command hierarchy 2.2 Implement Core Infrastructure Create shared utilities: API client with authentication Error handling helpers Response formatting (JSON/Markdown) Pagination support 2.3 Implement Tools For each tool: Input Schema: Use Zod (TypeScript) or Pydantic (Python) Include constraints and clear descriptions Add examples in field descriptions Output Schema: Define outputSchema where possible for structured data Use structuredContent in tool responses (TypeScript SDK feature) Helps clients understand and process tool outputs Tool Description: Concise summary of functionality Parameter descriptions Return type schema Implementation: Async/await for I/O operations Proper error handling with actionable messages Support pagination where applicable Return both text content and structured data when using modern SDKs Annotations: readOnlyHint : true/false destructiveHint : true/false idempotentHint : true/false openWorldHint : true/false Phase 3: Review and Test 3.1 Code Quality Review for: No duplicated code (DRY principle) Consistent error handling Full type coverage Clear tool descriptions 3.2 Build and Test TypeScript: Run npm run build to verify compilation Test with MCP Inspector: npx @modelcontextprotocol/inspector Python: Verify syntax: python -m py_compile your_server.py Test with MCP Inspector See language-specific guides for detailed testing approaches and quality checklists. Phase 4: Create Evaluations After implementing your MCP server, create comprehensive evaluations to test its effectiveness. Load ✅ Evaluation Guide for complete evaluation guidelines. 4.1 Understand Evaluation Purpose Use evaluations to test whether LLMs can effectively use your MCP server to answer realistic, complex questions. 4.2 Create 10 Evaluation Questions To create effective evaluations, follow the process outlined in the evaluation guide: Tool Inspection : List available tools and understand their capabilities Content Exploration : Use READ-ONLY operations to explore available data Question Generation : Create 10 complex, realistic questions Answer Verification : Solve each question yourself to verify answers 4.3 Evaluation Requirements Ensure each question is: Independent : Not dependent on other questions Read-only : Only non-destructive operations required Complex : Requiring multiple tool calls and deep exploration Realistic : Based on real use cases humans would care about Verifiable : Single, clear answer that can be verified by string comparison Stable : Answer won't change over time 4.4 Output Format Create an XML file with this structure: < evaluation > < qa_pair > < question > Find discussions about AI model launches with animal codenames. One model needed a specific safety designation that uses the format ASL-X. What number X was being determined for the model named after a spotted wild cat? </ question > < answer > 3 </ answer > </ qa_pair > <!-- More qa_pairs... --> </ evaluation > Reference Files 📚 Documentation Library Load these resources as needed during development: Core MCP Documentation (Load First) MCP Protocol : Start with sitemap at https://modelcontextprotocol.io/sitemap.xml , then fetch specific pages with .md suffix 📋 MCP Best Practices - Universal MCP guidelines including: Server and tool naming conventions Response format guidelines (JSON vs Markdown) Pagination best practices Transport selection (streamable HTTP vs stdio) Security and error handling standards Microsoft MCP Documentation (For Azure/Foundry) 🔷 Microsoft MCP Patterns - Microsoft-specific patterns including: Azure MCP Server architecture (48+ Azure services) C#/.NET command implementation patterns Remote MCP with Foundry Agent Service Authentication (Entra ID, OBO flow, Managed Identity) Testing infrastructure with Bicep templates SDK Documentation (Load During Phase 1/2) Python SDK : Fetch from https://raw.githubusercontent.com/modelcontextprotocol/python-sdk/main/README.md TypeScript SDK : Fetch from https://raw.githubusercontent.com/modelcontextprotocol/typescript-sdk/main/README.md Microsoft MCP SDK : See Microsoft MCP Patterns for C#/.NET Language-Specific Implementation Guides (Load During Phase 2) 🐍 Python Implementation Guide - Complete Python/FastMCP guide with: Server initialization patterns Pydantic model examples Tool registration with @mcp.tool Complete working examples Quality checklist ⚡ TypeScript Implementation Guide - Complete TypeScript guide with: Project structure Zod schema patterns Tool registration with server.registerTool Complete working examples Quality checklist 🔷 Microsoft MCP Patterns - Complete C#/.NET guide with: Command hierarchy (BaseCommand → GlobalCommand → SubscriptionCommand) Naming conventions ( {Resource}{Operation}Command ) Option handling with .AsRequired() / .AsOptional() Azure Functions remote MCP deployment Live test patterns with Bicep Evaluation Guide (Load During Phase 4) ✅ Evaluation Guide - Complete evaluation creation guide with: Question creation guidelines Answer verification strategies XML format specifications Example questions and answers Running an evaluation with the provided scripts