Borrowing it
Nothing to install: this file belongs to utensils/mcp-nixos. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/utensils/mcp-nixos/main/AGENTS.mdgit clone --depth 1 https://github.com/utensils/mcp-nixosWrote 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/instructions/utensils/mcp-nixos/agents-md)<a href="https://agentmods.dev/instructions/utensils/mcp-nixos/agents-md"><img src="https://agentmods.dev/badge/instructions/utensils/mcp-nixos/agents-md/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.
<a href="https://agentmods.dev/instructions/utensils/mcp-nixos/agents-md"><img src="https://agentmods.dev/badge/instructions/utensils/mcp-nixos/agents-md.svg" alt="Reviewed on agentmods" width="80" 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 | $0.02802 | $0.02802 |
| Opus 5.5 | $0.01121 | $0.01121 |
| Sonnet 5.5 | $0.00560 | $0.00560 |
| Haiku 4.5 | $0.00280 | $0.00280 |
Grade A, and why
mcp-nixos AGENTS.md 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.
This is a copy
100% identical to skills AGENTS.md — 198 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 — 197 lines — stays where its author put it; the contents beside it link to each section on GitHub.
CLAUDE.md
This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
Project Overview
MCP-NixOS is a Model Context Protocol (MCP) server that provides accurate, real-time information about NixOS packages, configuration options, Home Manager, nix-darwin, Nixvim, NVF, and flakes. It prevents AI assistants from hallucinating about NixOS package names and configurations by querying official APIs and documentation.
Project Structure & Module Organization
mcp_nixos/- Contains the MCP server implementation.mcp_nixos/server.py- MCP tools, tool routing, and main entry point.mcp_nixos/config.py- Configuration constants (API URLs, auth, limits).mcp_nixos/caches.py- Process-local cache implementations (channels, nixvim, NVF, noogle, nix.dev).mcp_nixos/utils.py- Shared utility functions (HTML parsing, formatting, file I/O).mcp_nixos/sources/- Data source implementations (one module per source):base.py- Channel helpers, Elasticsearch queries, browsing utilities.nixos.py- NixOS packages/options search, info, stats.home_manager.py- Home Manager options.darwin.py- nix-darwin options.flakes.py- Flake search from search.nixos.org.flakehub.py- FlakeHub API (Determinate Systems).wiki.py- NixOS Wiki search.nixdev.py- nix.dev documentation.nixvim.py- Nixvim options.nvf.py- NVF options, path normalization, and query actions.noogle.py- Noogle function search.nixhub.py- NixHub API + binary cache status.flake_inputs.py- Local flake inputs via nix store.
tests/- Holds pytest unit and integration tests; markers live inpytest.iniandtests/conftest.py.website/- The VitePress docs/marketing site (index.md,usage.md,about.md, custom theme under.vitepress/); static assets live inwebsite/public/. Output builds towebsite/out/and deploys to S3/CloudFront viadeploy-website.yml..pi/- Pi Coding Agent extension that wraps the MCP tools as native Pi tools (Pi does not speak MCP).extensions/mcp-nixos.tsspawns a Python subprocess that importsmcp_nixos.serverand calls the tool functions directly — not part of the MCP server runtime, only relevant when runningpiin this repo.flake.nix- Defines the Nix dev shell, package, overlays, and checks.nix/- Python package-set extension that vendors the FastMCP 4 / MCP SDK 2 stack (fastmcp4.nixplus one pure-Python wheel derivation per package, e.g.fastmcp.nix,mcp.nix,starlette.nix) for nixpkgs pins that still ship older releases.flake.nixapplies it scoped topkgs.mcp-nixosviaoverrideScope, and exports it set-wide asoverlays.fastmcp4.pyproject.toml- Defines Python packaging and dependencies.dist/,htmlcov/, andresult/are generated artifacts; do not edit by hand.
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 Changed · +196 lines · +2,798 tokens per session 4f07c6709659
- 2mo ago First seen · 1 lines · 4 tokens per session scan A 6ebdb617a810
mcp-nixos AGENTS.md is an instructions file published in the GitHub repository utensils/mcp-nixos (876 stars, last pushed 10d ago), licensed MIT. It adds 2,802 tokens to every session, about $0.0112 per session on Opus 5.5. A static security scan graded it A with 0 findings. It is 100% identical to skills AGENTS.md, differing in 198 lines, and is treated as a copy.
Other instructions, from other repositories
vscode buildNext.instructions.md
Working notes and architecture documentation for the new esbuild-based build system in build/next. Use when making changes to the new build pipeline (transpile/bundle commands, NLS plugin, source-map handling, resource copying, or self-hosting watch tasks).
next.js AGENTS.md
AGENTS.md instructions for vercel/next.js, covering next.js development guide, codebase structure, monorepo overview, core package: packages/next and other important packages.
vscode oss-third-party-notices.instructions.md
Instructions for microsoft/vscode, covering vs code oss third-party-notices pipeline, architecture, pipeline flow in ci, cache eligibility and rollout and applying the notice (cutover).
langchain AGENTS.md
AGENTS.md instructions for langchain-ai/langchain, covering global development guidelines for the langchain monorepo, corridor security analysis, project architecture and context, monorepo structure and development tools & commands.
deepseek-harness AGENTS.md
AGENTS.md instructions for deepseek-ai/deepseek-harness, covering agents.md, pre-stable apis and released session data, repository layout, commands and host sandbox failures.
vscode copilot-instructions.md
Copilot instructions for microsoft/vscode, covering vs code copilot instructions, project overview, root folders, core architecture (src/ folder) and built-in extensions (extensions/ folder).