mcp-builder
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) or Node/TypeScript (MCP SDK).
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MCP Builder - Complete Guide to MCP Server Development
Overview
MCP Builder is a comprehensive guide to developing MCP (Model Context Protocol) servers, helping developers create high-quality MCP servers that enable LLMs to interact with external services through carefully designed tools.
Use Cases
When you need AI applications to call third-party APIs (such as GitHub, databases, or payment services), MCP Builder provides a standardized development workflow covering end-to-end guidance from protocol research to tool design.
When building a callable tooling layer for LLMs like Claude, this guide covers key design elements such as tool naming conventions, input/output schema definitions, and error handling to ensure tools are AI-friendly and easy to invoke.
After development, to verify whether LLMs can effectively use your MCP server, the guide provides methods for creating evaluation prompts, including design standards for test cases covering 10 complex scenarios.
Core Features
Breaks MCP server development into four stages: research & planning → implementation → code review → evaluation & testing. Each stage has clear checklists and deliverables to avoid missing critical steps.
Provides full implementation examples for a TypeScript SDK (recommended) and Python FastMCP, including project structure, Zod/Pydantic schema definitions, tool registration, and other practical code snippets ready for reuse.
Includes interpretations of the official MCP specification, covering server naming, response formats (JSON vs Markdown), pagination design, transport choices (streamable HTTP vs stdio), and other guidelines to ensure servers meet industry standards.
Frequently Asked Questions
What is an MCP server? What is it used for?
An MCP (Model Context Protocol) server is a standardized interface that allows LLMs to interact with external systems via defined "tools." For example, you can create an MCP server that enables Claude to read GitHub issues, query databases, or call payment APIs.
How to choose TypeScript or Python for developing an MCP server?
TypeScript is recommended because: (1) SDK support is more mature; (2) AI models are better at generating TypeScript code; (3) static typing and linting tools are mature. If your team already uses a Python stack, FastMCP is also a viable option, and the documentation includes complete Pydantic model examples.
How to define input/output schemas for MCP tools?
In TypeScript, use Zod; in Python, use Pydantic to define schemas. Input schemas should include field types, constraints, and clear descriptions; output schemas should use outputSchema to define structured data and be returned with structuredContent so clients can better interpret the results.
What is MCP evaluation? Why create evaluation prompts?
MCP evaluation is a method to test whether LLMs can effectively use your server to answer complex questions. You should create 10 independent, read-only, multi-tool-invocation real-world scenario questions and verify the answers yourself. This helps uncover blind spots in tool design and ensures the server is reliable and effective in real use.