A guide for building Model Context Protocol servers, which let Claude use external tools and data through a standard connection. It covers callable tools, readable resources, and reusable prompts.

Use it to create an MCP server in Python or TypeScript, expose functions to Claude, connect outside services, or provide Claude with structured data and prompt templates.

It helps turn an external service or data source into clearly defined actions Claude can use. It also addresses input checks, useful errors, asynchronous operations, security, and safe repeatable calls.

mcp-builder — Skill for Claude Code and Codex by Chris-debug-0225

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent

npx skills add Chris-debug-0225/learn-claude-code-java --skill mcp-builder

Clone the repo

git clone --depth 1 https://github.com/Chris-debug-0225/learn-claude-code-java

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

README.md

[![agentmods](https://agentmods.dev/badge/skills/chris-debug-0225/learn-claude-code-java/mcp-builder/github.svg)](https://agentmods.dev/skills/chris-debug-0225/learn-claude-code-java/mcp-builder)

Your own site

<a href="https://agentmods.dev/skills/chris-debug-0225/learn-claude-code-java/mcp-builder"><img src="https://agentmods.dev/badge/skills/chris-debug-0225/learn-claude-code-java/mcp-builder/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

Your own site · 80×15

<a href="https://agentmods.dev/skills/chris-debug-0225/learn-claude-code-java/mcp-builder"><img src="https://agentmods.dev/badge/skills/chris-debug-0225/learn-claude-code-java/mcp-builder.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 38 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 308 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

Origin original No closer match found in the catalogue.

Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

Model	Per session	Once invoked
Fable 5.1	$0.00038	$0.00308
Opus 5.5	$0.00015	$0.00123
Sonnet 5.5	$0.00008	$0.00062
Haiku 4.5	$0.00004	$0.00031

Measured 2mo ago against content hash bffd183c7805, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

mcp-builder scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2mo ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/mcp-builder/SKILL.md · 49 lines

What it actually says

MCP Server Building Skill

You now have expertise in building MCP (Model Context Protocol) servers. MCP enables Claude to interact with external services through a standardized protocol.

What is MCP?

MCP servers expose:

Tools: Functions Claude can call
Resources: Data Claude can read
Prompts: Pre-built prompt templates

Quick Start: Python MCP Server

from mcp.server import Server
from mcp.server.stdio import stdio_server

server = Server("my-server")

@server.tool()
async def hello(name: str) -> str:
    return f"Hello, {name}!"

TypeScript MCP Server

import { Server } from "@modelcontextprotocol/sdk/server/index.js";
import { StdioServerTransport } from "@modelcontextprotocol/sdk/server/stdio.js";

const server = new Server({ name: "my-server", version: "1.0.0" });
const transport = new StdioServerTransport();
server.connect(transport);

Best Practices

Clear tool descriptions
Input validation
Meaningful error handling
Async for I/O
Security first
Idempotent tools when possible

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

2mo ago First seen · 49 lines · 38 tokens per session scan A bffd183c7805

Subscribe to this mod's changes

mcp-builder is a skill published in the GitHub repository Chris-debug-0225/learn-claude-code-java (108 stars, last pushed 7mo ago), licensed MIT. It adds 38 tokens to every session and 308 once invoked, about $0.0002 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

Building agents

mcp-builder next to 6 skills from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
mcp-builderChris-debug-0225/learn-claude-code-java	Skill	108	7mo ago	MIT	A	38	Claude Code, Codex
imagegenopenai/codex	Skill	133k	yesterday	Apache-2.0	A	113	Codex
playwright-climicrosoft/playwright	Skill	99k	yesterday	Apache-2.0	A	19	Claude Code
local-ai-agentsmicrosoft/ai-agents-for-beginners	Skill	79k	4d ago	MIT	A	200	Claude Code, Codex
systematic-debuggingobra/superpowers	Skill	313k	3d ago	MIT	A	21	Claude Code
next-cache-components-adoptionvercel/next.js	Skill	143k	yesterday	MIT	A	95	Claude Code
next-partial-prefetching-adoptionvercel/next.js	Skill	143k	yesterday	MIT	A	103	Claude Code