What it does
A guide skill for building high-quality MCP servers (Model Context Protocol) — the layer through which an LLM talks to external services. It walks you through four phases: research and planning (design principles, framework choice, with TypeScript + Streamable HTTP preferred) → implementation (project structure, tool schemas, error handling, pagination) → review and tests (MCP Inspector, type coverage) → evals (10 realistic, hard scenarios that prove an LLM can actually use the server). It has a dual nature: a skill about the MCP ecosystem that is itself a skill.
How to set it up
It ships in the example-skills bundle:
/plugin install example-skills@anthropic-agent-skills
Or drop the mcp-builder/ folder into ~/.claude/skills/. In Claude Code it shows up as the mcp-builder skill.
When to use it
- You need to wrap your own API or service in an MCP server that an agent will genuinely use.
- You want sound tool design and test scenarios from the start rather than a raw server.
Example
"Build an MCP server for our billing API" — the skill designs the tools with clear schemas and error messages, implements them in TS and sketches out 10 eval scenarios.