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).
What it does
Claude generates MCP servers that don't conform to the spec: tools with missing or incorrect JSON Schema for inputs, resources with malformed URI patterns, improper error handling that crashes the server instead of returning a structured error, and server configurations that don't work with Claude Desktop or Claude Code. This skill loads the correct MCP implementation patterns for both Python (FastMCP) and TypeScript (MCP SDK) — tools, resources, prompts, and the configuration files needed to connect them to a client.
Use case
Building an MCP server to expose an API, database, or service to Claude. The failure mode this prevents: an MCP server that starts without errors but whose tools don't appear in Claude, or appear but error on every call. Made by Anthropic.
"Build an MCP server that exposes my company's Jira API as tools for Claude." "Create an MCP resource that gives Claude read access to our internal docs." "My MCP tool isn't showing up in Claude — diagnose the implementation." "Add a Slack tool that lets Claude post to a specific channel." "Build a filesystem MCP server restricted to a specific directory."
Describe the service or API you want to expose and which operations Claude should perform.
Specify Python or TypeScript — both are fully supported.
Claude generates a complete, runnable server with the claude_desktop_config.json or .claude/settings.json entry needed to connect it.
Input
A description of the external service, its authentication pattern, and the operations you want Claude to perform.
Output
A complete MCP server with correctly defined tools (proper JSON Schema inputs), resources (correct URI patterns), and configuration for Claude Desktop or Claude Code. Runnable immediately.
npx skillsadd anthropics/skills/mcp-builder
npx skillsadd anthropics/skills/mcp-builder
Requires skills.sh CLI
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