mcp-builder

mcp-builder is a skill for Claude Code from alleneee/skill-agent. It costs 61 tokens per session (2,865 once invoked), scanned A, original, no licence file.

A guide to building MCP servers, which are services that let language models use tools connected to outside systems. It covers integrations built in Python with FastMCP or in Node.js and TypeScript with the MCP SDK.

In plain words
What is it for?
Use it when building an MCP server to connect a language model with an external API, service, or agent.
Why use it?
It helps turn an outside API or agent into clearly designed tools that a language model can call. This avoids having to work out the server structure and tool design from scratch.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin.

Part of the example-skills plugin — 9 skills shipped together

Good fit Use it when building an MCP server to connect a language model with an external API, service, or agent.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/alleneee/skill-agent/mcp-builder
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 alleneee/skill-agent --skill mcp-builder
Clone the repo
git clone --depth 1 https://github.com/alleneee/skill-agent

Made for: Claude Code.

Or install example-skills, the plugin that ships this one along with the rest of its 9 skills.

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/alleneee/skill-agent/mcp-builder/github.svg)](https://agentmods.dev/skills/alleneee/skill-agent/mcp-builder)
Your own site
<a href="https://agentmods.dev/skills/alleneee/skill-agent/mcp-builder"><img src="https://agentmods.dev/badge/skills/alleneee/skill-agent/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/alleneee/skill-agent/mcp-builder"><img src="https://agentmods.dev/badge/skills/alleneee/skill-agent/mcp-builder.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 61 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,865 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. Third-party audits
  • Socket pass 13 Apr 2026
  • Snyk warn 13 Apr 2026
How audits are shown
Origin unknown 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 $0.00061 $0.02865
Opus 5.5 $0.00024 $0.01146
Sonnet 5.5 $0.00012 $0.00573
Haiku 4.5 $0.00006 $0.00286

Measured 1mo ago against content hash ccefd2812b54, 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 1mo ago.

The scan reads SKILL.md. This mod also ships 2 executable files (scripts/connections.py, scripts/evaluation.py), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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.

src/omni_agent/skills/mcp-builder/SKILL.md · 329 lines

The source is not reproduced here

No licence file

A repository with no LICENSE is all rights reserved by default, so the body is not copied here. The metadata, the measurements and the link are.

Read it on GitHub

Files

What ships with it

9 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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. 1mo ago First seen · 329 lines · 61 tokens per session scan A ccefd2812b54

Subscribe to this mod's changes

mcp-builder is a skill published in the GitHub repository alleneee/skill-agent (27 stars, last pushed 7mo ago), with no licence file. It adds 61 tokens to every session and 2,865 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.

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