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mcp-server: Instructions file for Claude Code

CLAUDE.md

mcp-server CLAUDE.md is an instructions file for Claude Code from mackerelio-labs/mcp-server. It costs 466 tokens per session, scanned A, original, Apache-2.0.

Repository instructions for a TypeScript MCP server that exposes Mackerel, a service-monitoring platform, to AI assistants through the Model Context Protocol. They cover its tools, tests, mocks, and development commands.

In plain words
What is it for?
Use them to add or edit Mackerel API tools, build or run the server, test API interactions with mocks, and check code formatting.
Why use it?
They explain how the server is organized and which commands verify that its API tools and formatting still work.

Instructions file for Claude Code

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

This is mackerelio-labs/mcp-server's own configuration. It tells Claude Code how to work on mcp-server 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 mcp-server configures →

not rated 7repo today A scan 466 tokens original Apache-2.0
View source ↗ mackerelio-labs/mcp-server
Reuse

Borrowing it

Nothing to install: this file belongs to mackerelio-labs/mcp-server. 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/mackerelio-labs/mcp-server/main/CLAUDE.md
Clone the repo
git clone --depth 1 https://github.com/mackerelio-labs/mcp-server

Made for: Claude Code.

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Per session 466 This file is loaded in full into every session.
When invoked 466 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 $0.00466 $0.00466
Opus 5 $0.00233 $0.00233
Sonnet 5 $0.00093 $0.00093
Haiku 4.5 $0.00047 $0.00047

Measured 8d ago against content hash cc912ff057b6, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-07, from the pricing page.

Security

Grade A, and why

mcp-server 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 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.

CLAUDE.md · 50 lines

How it starts

The opening of the file, as written. The whole thing — 50 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

This is a Mackerel MCP (Model Context Protocol) server that provides tools for interacting with the Mackerel API. The server exposes Mackerel functionality as MCP tools that can be used by AI assistants.

Development Commands

  • npm run build - Compile TypeScript to JavaScript
  • npm run dev - Run the server directly via stdio transport
  • npm run test - Run tests with Vitest
  • npm run format - Format code with Prettier
  • npm run format:check - Check code formatting

Architecture

src/
├── index.ts              # Main MCP server entry point - registers tools and starts stdio transport
├── tools/                # MCP tool implementations
├── mocks/                # MSW mock server setup for testing
└── __tests__/            # Test utilities and setup
  • src/index.ts - Main server entry point that registers tools and starts stdio transport
  • src/tools/ - Individual MCP tool implementations following a consistent pattern
  • src/mocks/ - MSW mock server setup for testing API interactions
  • src/tests/ - Shared test utilities and setup helpers

Tool Development Pattern

Each tool follows this structure:

  1. Refer https://mackerel.io/api-docs/ for API documentation
  2. Define Zod schema for input validation that includes ALL documented parameters
  3. Implement tool callback that builds URLSearchParams for API calls
  4. Use buildToolResponse() utility for consistent response formatting and error handling
  5. Tools are registered in src/index.ts
  6. Tests are written next to the tool implementation
  7. Add the tool to the Available tools section in the README

Notes:

  • About API Documentation Reference: When viewing API documentation, first visit https://mackerel.io/api-docs/ and follow the endpoint links listed there to check the detailed specifications for the target endpoint.

Testing

Read the full file on GitHub · 50 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 · 50 lines · 466 tokens per session scan A cc912ff057b6

Subscribe to this mod's changes

mcp-server CLAUDE.md is an instructions file published in the GitHub repository mackerelio-labs/mcp-server (7 stars, last pushed today), licensed Apache-2.0. It adds 466 tokens to every session, about $0.0023 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 2026-08-31.

PlanningTypeScriptmackerelmcpmcp-server
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