mcp-builder

mcp-builder is a skill for Claude Code, Codex from fabioc-aloha/Alex_Skill_Mall. It costs 38 tokens per session (2,204 once invoked), scanned A, original, MIT.

A guide to building MCP servers, which let AI assistants call tools and work with outside services through a common interface.

In plain words
What is it for?
Use it to create MCP servers in Python, TypeScript, or C# for custom APIs, SaaS services, and other tool integrations.
Why use it?
It helps developers connect custom internal APIs or third-party services to AI assistants without designing a separate integration for each client.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Needs its repository: it runs a file that does not travel with it, so clone the repository first. The line is npx @modelcontextprotocol/inspector ./dist/server.js.

Good fit Use it to create MCP servers in Python, TypeScript, or C# for custom APIs, SaaS services, and other tool integrations.

Compare 6 skills from other repositories ↓
Install

Getting it into your agent

It runs from inside its repository, so the clone comes first — what it calls does not travel with the file alone.

Clone the repo
git clone --depth 1 https://github.com/fabioc-aloha/Alex_Skill_Mall
agentmods
npx agentmods add skills/fabioc-aloha/alex_skill_mall/mcp-builder

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.

agentmods badge for mcp-builder

README.md
[![agentmods](https://agentmods.dev/badge/skills/fabioc-aloha/alex_skill_mall/mcp-builder/github.svg)](https://agentmods.dev/skills/fabioc-aloha/alex_skill_mall/mcp-builder)
Your own site
<a href="https://agentmods.dev/skills/fabioc-aloha/alex_skill_mall/mcp-builder"><img src="https://agentmods.dev/badge/skills/fabioc-aloha/alex_skill_mall/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.

agentmods 80×15 button for mcp-builder

Your own site · 80×15
<a href="https://agentmods.dev/skills/fabioc-aloha/alex_skill_mall/mcp-builder"><img src="https://agentmods.dev/badge/skills/fabioc-aloha/alex_skill_mall/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 2,204 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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00038 $0.02204
Opus 5 $0.00019 $0.01102
Sonnet 5 $0.00008 $0.00441
Haiku 4.5 $0.00004 $0.00220

Measured 8d ago against content hash 827bf30cedf0, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, 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 8d 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.

plugins/ai-agents/mcp-builder/skills/mcp-builder/SKILL.md · 324 lines

How it starts

The opening of the file, as written. The whole thing — 324 lines — stays where its author put it; the contents beside it link to each section on GitHub.

MCP Server Development Guide

Build high-quality MCP servers that enable LLMs to interact with external services

Staleness Watch: See EXTERNAL-API-REGISTRY.md for source URLs and recheck cadence

The quality of an MCP server is measured by how well it enables LLMs to accomplish real-world tasks.


When to Build vs Use Existing

Microsoft MCP Servers

Before building custom, check if Microsoft already provides one:

Server Type Description
Azure MCP Local 48+ Azure services (Storage, KeyVault, Cosmos, SQL, etc.)
Foundry MCP Remote https://mcp.ai.azure.com - Models, deployments, evals, agents
Fabric MCP Local Microsoft Fabric APIs, OneLake, item definitions
Playwright MCP Local Browser automation and testing
GitHub MCP Remote https://api.githubcopilot.com/mcp

Decision Matrix

Scenario Recommendation
Azure service integration Use Azure MCP Server (48 services covered)
AI Foundry agents/evals Use Foundry MCP remote server
Custom internal APIs Build custom server (this guide)
Third-party SaaS integration Build custom server (this guide)

Server Types

Type Transport Use Case Example
Local stdio Desktop apps, single-user, local dev Azure MCP Server via NPM/Docker
Remote Streamable HTTP Cloud services, multi-tenant, Agent Service https://mcp.ai.azure.com (Foundry)

Phase 1: Research and Planning

1.1 Understand Modern MCP Design

API Coverage vs. Workflow Tools: Balance comprehensive API endpoint coverage with specialized workflow tools. When uncertain, prioritize comprehensive API coverage.

Tool Naming and Discoverability: Clear, descriptive tool names help agents find the right tools quickly. Use consistent prefixes (e.g., github_create_issue, github_list_repos) and action-oriented naming.

Read the full file on GitHub · 324 lines

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.

  1. 8d ago First seen · 324 lines · 38 tokens per session scan A 827bf30cedf0

Subscribe to this mod's changes

mcp-builder is a skill published in the GitHub repository fabioc-aloha/Alex_Skill_Mall (4 stars, last pushed yesterday), licensed MIT. It adds 38 tokens to every session and 2,204 once invoked, about $0.0002 per session on Opus 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 2026-09-03.

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