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preact-mcp: Instructions file for Claude Code

CLAUDE.md

preact-mcp CLAUDE.md is an instructions file for Claude Code from JoviDeCroock/preact-mcp. It costs 1,392 tokens per session, scanned A, original, MIT.

Project instructions and technical notes for a server that gives Claude access to Preact documentation. Preact is a lightweight JavaScript interface library, and MCP is a standard way for AI tools to access external data.

In plain words
What is it for?
Useful when changing the Preact documentation server, its GitHub data fetching and caching, or its documentation-search tools.
Why use it?
They give the coding agent the project’s structure, data sources, and expected behavior, so it can work on the server with the right context.

Instructions file for Claude Code

Written for Claude Code: the file is CLAUDE.md. Also seen: mentions Claude Code.

This is JoviDeCroock/preact-mcp's own configuration. It tells Claude Code how to work on preact-mcp itself, so it is not a mod to install elsewhere. Copy it as a starting point and replace the rules that are about this project. Everything preact-mcp configures →

not rated 2repo 1y ago A scan 1,392 tokens original MIT
View source ↗ JoviDeCroock/preact-mcp
Reuse

Borrowing it

Nothing to install: this file belongs to JoviDeCroock/preact-mcp. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file
curl -O https://raw.githubusercontent.com/JoviDeCroock/preact-mcp/main/CLAUDE.md
Clone the repo
git clone --depth 1 https://github.com/JoviDeCroock/preact-mcp

Made for: Claude Code.

Wrote this? Show the measurements

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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.

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Per session 1,392 This file is loaded in full into every session.
When invoked 1,392 The same file — it is already loaded in full.
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 $0.01392 $0.01392
Opus 5.5 $0.00557 $0.00557
Sonnet 5.5 $0.00278 $0.00278
Haiku 4.5 $0.00139 $0.00139

Measured 2mo ago against content hash 8eaf51cc0765, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

preact-mcp CLAUDE.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.

CLAUDE.md · 202 lines

How it starts

The opening of the file, as written. The whole thing — 202 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Claude Documentation - Preact MCP Server

This document contains technical details and learnings about the Preact MCP Server implementation for Claude Code.

Project Overview

The Preact MCP Server is a Model Context Protocol implementation that provides Claude with access to Preact ecosystem documentation. It aggregates information from multiple Preact repositories to answer questions about Preact, Preact-ISO, and Signals.

Architecture

Core Components

1. MCP Server (src/index.ts)
  • Purpose: Main server implementation using the MCP SDK
  • Key Features:
    • Stdio transport for communication with Claude
    • Tool registration and request handling
    • Error handling and validation
  • Tools Exposed:
    • query_preact_docs: Multi-repository documentation search
    • get_preact_readme: Repository-specific README retrieval
    • list_preact_repositories: Available repository enumeration
2. Data Source (src/datasource.ts)
  • Purpose: Handles data fetching and caching from GitHub
  • Key Features:
    • HTTP caching with 5-minute TTL to respect rate limits
    • Text search with context extraction
    • Error handling for network failures
    • Support for multiple repository sources

Repository Sources

The server queries these Preact ecosystem repositories:

  1. preact/preact: Core Preact library

    • README: https://raw.githubusercontent.com/preactjs/preact/refs/heads/main/README.md
    • Description: Fast 3kB React alternative

  2. preact/preact-iso: Isomorphic utilities

    • README: https://raw.githubusercontent.com/preactjs/preact-iso/refs/heads/main/README.md
    • Description: SSR and hydration utilities

  3. preact/signals: Reactive state management

    • README: https://raw.githubusercontent.com/preactjs/signals/refs/heads/main/README.md
    • Description: Fine-grained reactivity system

Technical Implementation Details

Search Algorithm

  • Performs case-insensitive substring matching
  • Returns context (2 lines before/after matches)
  • Limits results to 10 matches per repository
  • Formats results with markdown code blocks

Read the full file on GitHub · 202 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. 2mo ago First seen · 202 lines · 1,392 tokens per session scan A 8eaf51cc0765

Subscribe to this mod's changes

preact-mcp CLAUDE.md is an instructions file published in the GitHub repository JoviDeCroock/preact-mcp (2 stars, last pushed 1y ago), licensed MIT. It adds 1,392 tokens to every session, about $0.0056 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 2026-08-31.

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