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.
npx agentmods add skills/malob/nix-config/mcp-buildernpx skills add malob/nix-config --skill mcp-buildergit clone --depth 1 https://github.com/malob/nix-configWrote 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.
[](https://agentmods.dev/skills/malob/nix-config/mcp-builder)<a href="https://agentmods.dev/skills/malob/nix-config/mcp-builder"><img src="https://agentmods.dev/badge/skills/malob/nix-config/mcp-builder.svg" alt="Measured on agentmods" height="20"></a>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 | $0.00061 | $0.01938 |
| Opus 5 | $0.00030 | $0.00969 |
| Sonnet 5 | $0.00012 | $0.00388 |
| Haiku 4.5 | $0.00006 | $0.00194 |
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 6d 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.
This is a copy
100% identical to mcp-builder — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 237 lines — stays where its author put it; the contents beside it link to each section on GitHub.
MCP Server Development Guide
Overview
Create MCP (Model Context Protocol) servers that enable LLMs to interact with external services through well-designed tools. The quality of an MCP server is measured by how well it enables LLMs to accomplish real-world tasks.
Process
🚀 High-Level Workflow
Creating a high-quality MCP server involves four main phases:
Phase 1: Deep Research and Planning
1.1 Understand Modern MCP Design
API Coverage vs. Workflow Tools: Balance comprehensive API endpoint coverage with specialized workflow tools. Workflow tools can be more convenient for specific tasks, while comprehensive coverage gives agents flexibility to compose operations. Performance varies by client—some clients benefit from code execution that combines basic tools, while others work better with higher-level workflows. 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.
Context Management: Agents benefit from concise tool descriptions and the ability to filter/paginate results. Design tools that return focused, relevant data. Some clients support code execution which can help agents filter and process data efficiently.
Actionable Error Messages: Error messages should guide agents toward solutions with specific suggestions and next steps.
1.2 Study MCP Protocol Documentation
Navigate the MCP specification:
Start with the sitemap to find relevant pages: https://modelcontextprotocol.io/sitemap.xml
Then fetch specific pages with .md suffix for markdown format (e.g., https://modelcontextprotocol.io/specification/draft.md).
Key pages to review:
- Specification overview and architecture
- Transport mechanisms (streamable HTTP, stdio)
- Tool, resource, and prompt definitions
1.3 Study Framework Documentation
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.
- LICENSE.txt 11 KB
- reference/evaluation.md 21 KB
- reference/mcp_best_practices.md 7.2 KB
- reference/node_mcp_server.md 28 KB
- reference/python_mcp_server.md 25 KB
- scripts/connections.py 4.8 KB runs code
- scripts/evaluation.py 12 KB runs code
- scripts/example_evaluation.xml 1.2 KB
- scripts/requirements.txt 29 B
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.
- 6d ago First seen · 237 lines · 61 tokens per session scan A 0f4592dcb53c
mcp-builder is a skill published in the GitHub repository malob/nix-config (462 stars, last pushed 6d ago), licensed MIT. It adds 61 tokens to every session and 1,938 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. It is 100% identical to mcp-builder, differing in 0 lines, and is treated as a copy.
Other skills, from other repositories
restart__pull_request
乱れた (fix-up コミット過多・議論の脱線・大規模な書き直し) プルリクエストを、 ユーザーが "restart" / "やり直し" したいときに起動する。既存 PR を close し、 ブランチを新ブランチ上の単一のクリーンなコミットに squash し、過去の PR 議論 (レビューコメント・スレッド・リアクション) を統合した説明文で新しい PR を作成する。 元のブランチを force-push してはならない。必ず新しいブランチを作成する。.
validate__japanese
日本語の Markdown 文書 (README・ドキュメント・ブログ下書き・.md) を編集した後に起動する。textlint の ja-technical-writing / ja-spacing プリセットで、長すぎる一文・読点過多・文体の混在・全角半角スペースを検出する。さらに文中ハードラップ (文末でない位置で折り返した、意味のない改行) を検出し、段落・箇条書き項目を 1 行に連結して調整する。1 行に文を積み上げた箇所は、箇条書きへの変換候補として検出する。実在のシンボルを指すコードスニペットへ参照リンクも付与する。日本語の .md を変更したときに使用する。.
clean__comment_out
ソースコードを編集・作成した後に起動する。変更したファイルから、共有 whitelist マーカー (TODO/FIXME/SEE/CONSTRAINT/NOTE/HACK/SAFETY) で始まらない非 doc コメントを すべて削除する。What コメント・汎用 Why・コメントアウトされたデッドコード・ legacy XXX・CONSTRAINT に紐付かない単独 REASON: 行などマーカーの無いコメントは削除し、 whitelist マーカーで始まるコメントと CONSTRAINT に続く REASON: 継続行と 公開インターフェースのドキュメンテーションコメント (rustdoc ///…
implement__feature
実装タスクを 3 段階で自律遂行するときに起動する。Phase 1 で実装計画と テストリストを立案して skeptical-reviewer の反証評価を通し、Phase 2 で Sonnet 5 モデル固定のサブエージェント tdd-implementer に作業単位ごとの TDD 実装を委譲し、Phase 3 で reviewcode シリーズによるコードレビューを 全 pass または 3 回の反復まで実施する。.
prepare__issue
あなたは要件定義済みの Issue を実装着手可能な状態へ引き上げるオーケストレーターである。 対象は status:acknowledged の Issue であり、完了時に status:ready へ遷移させる。.
rescue__pull_request_review
GitHub PR にレビュアー (人間または AI) がコメントを残した後に起動する。 レビューコメントを読み取り、要求されたコード変更を適用し、コミットして push する。 レビューフィードバックの各ラウンドごとに繰り返す。ユーザーの確認は不要 — Claude がこのプロセス全体を自律的に起動・実行する。.