Mcp builder

Skill cskwork/claude-minimal-plugin/skills/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).From its SKILL.md

Install

npx -y skills add cskwork/claude-minimal-plugin --skill mcp-builder

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SKILL.md

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MCP Server Development Guide

Create MCP servers that enable LLMs to interact with external services through well-designed tools.

High-Level Workflow

Phase 1: Research and Planning

Understand Modern MCP Design:

Balance comprehensive API coverage with specialized workflow tools
Use clear, descriptive tool names with consistent prefixes (e.g., github_create_issue)
Design tools that return focused, relevant data
Provide actionable error messages

Study MCP Protocol:

Start with sitemap: https://modelcontextprotocol.io/sitemap.xml
Key pages: specification, transport mechanisms, tool definitions

Phase 2: Implementation

Recommended Stack:

Language: TypeScript (best SDK support)
Transport: Streamable HTTP for remote, stdio for local

Project Structure:

my-mcp-server/
├── src/
│   ├── index.ts      # Server entry point
│   ├── tools/        # Tool implementations
│   └── utils/        # Shared utilities
├── package.json
└── tsconfig.json

Tool Implementation Pattern:

server.registerTool({
  name: "github_create_issue",
  description: "Create a new GitHub issue",
  inputSchema: z.object({
    repo: z.string().describe("Repository name (owner/repo)"),
    title: z.string().describe("Issue title"),
    body: z.string().optional().describe("Issue body")
  }),
  outputSchema: z.object({
    id: z.number(),
    url: z.string()
  }),
  annotations: {
    readOnlyHint: false,
    destructiveHint: false,
    idempotentHint: false
  },
  handler: async (input) => {
    // Implementation
    return { id: 123, url: "https://..." };
  }
});

Phase 3: Test

# TypeScript
npm run build
npx @modelcontextprotocol/inspector

# Python
python -m py_compile your_server.py

Phase 4: Create Evaluations

Create 10 complex, realistic questions to test your MCP server:

<evaluation>
  <qa_pair>
    <question>Find all open issues labeled 'bug' in the repo</question>
    <answer>5</answer>
  </qa_pair>
</evaluation>

Tool Design Best Practices

Use Zod (TS) or Pydantic (Python) for schemas
Include constraints and examples in field descriptions
Define outputSchema for structured data
Support pagination where applicable
Add tool annotations (readOnly, destructive, idempotent)

What ships with it

Read from the repository

Just SKILL.md. No reference files, no scripts.