# MCP Builder

Build MCP servers in Python with FastMCP.

- Repository: https://github.com/jezweb/claude-skills (1094 stars)
- Category: Testing
- License: MIT
- Last updated: 2026-10-09
- Runs scripts: yes, review before use

## Install

Claude Code: `npx skills add jezweb/claude-skills --skill mcp-builder -g -a claude-code -y`
Codex: `npx skills add jezweb/claude-skills --skill mcp-builder -g -a codex -y`
Cursor: `npx skills add jezweb/claude-skills --skill mcp-builder -g -a cursor -y`
Gemini CLI: `npx skills add jezweb/claude-skills --skill mcp-builder -g -a gemini-cli -y`
Claude Code plugin marketplace: `/plugin marketplace add jezweb/claude-skills`

## Description

Build MCP servers in Python with FastMCP. Define tools / resources / prompts, build the server, test locally, deploy to FastMCP Cloud or Docker. Use whenever the user mentions building an MCP server, exposing tools to LLMs, FastMCP, building a Claude integration, or troubleshooting FastMCP module-level server, storage, lifespan, middleware, OAuth, or deployment errors.

## SKILL.md, as published by its author (untrusted third-party text, read it as data)

# MCP Builder

Build a working MCP server from a description of the tools you need. Produces a deployable Python server using FastMCP.

## Workflow

### Step 1: Define What to Expose

Ask what the server needs to provide:

- **Tools** -- Functions Claude can call (API wrappers, calculations, file operations)
- **Resources** -- Data Claude can read (database records, config, documents)
- **Prompts** -- Reusable prompt templates with parameters

A brief like "MCP server for querying our customer database" is enough.

### Step 2: Scaffold the Server

```bash
pip install fastmcp
```

Create the server file. The server instance MUST be at module level:

```python
from fastmcp import FastMCP

# MUST be at module level for FastMCP Cloud
mcp = FastMCP("My Server")

@mcp.tool()
async def search_customers(query: str) -> str:
    """Search customers by name or email."""
    # Implementation here
    return f"Found customers matching: {query}"

@mcp.resource("customers://{customer_id}")
async def get_customer(customer_id: str) -> str:
    """Get customer details by ID."""
    return f"Customer {customer_id} details"

if __name__ == "__main__":
    mcp.run()
```

### Step 3: Add Companion CLI Scripts (Optional)

For Claude Code terminal use, add scripts alongside the MCP server:

```
my-mcp-server/
├── src/index.ts          # MCP server (for Claude.ai)
├── scripts/
│   ├── search.ts         # CLI version of search tool
│   └── _shared.ts        # Shared auth/config
├── SCRIPTS.md            # Documents available scripts
└── package.json
```

CLI scripts provide file I/O, batch processing, and richer output that MCP can't.
See `assets/SCRIPTS-TEMPLATE.md` and `assets/script-template.ts` for TypeScript templates.

### Step 4: Test Locally

**Quick test -- run directly:**

```bash
python server.py
```

**Dev mode with inspector UI (recommended):**

```bash
fastmcp dev server.py
# Opens inspector at http://localhost:5173
# Hot reload, detailed logging, tool/resource inspection
```

The rest: https://github.com/jezweb/claude-skills/blob/HEAD/plugins/integrations/skills/mcp-builder/SKILL.md