What is mailtrap-mcp CLAUDE.md?

Repository guidance for Claude Code, an AI coding assistant, working on a Mailtrap email-service connector. It lists the main commands, project structure, code checks, and tests.

Running builds, development mode, lint checks, TypeScript checks, Jest tests, test coverage, and understanding where the connector's main files are.

It gives the coding assistant the project-specific instructions needed to build, inspect, and test the connector consistently.

How mailtrap/mailtrap-mcp configures Claude Code

Reuse

Borrowing it

Nothing to install: this file belongs to mailtrap/mailtrap-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/mailtrap/mailtrap-mcp/main/CLAUDE.md

Clone the repo

git clone --depth 1 https://github.com/mailtrap/mailtrap-mcp

Made for: Claude Code.

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.

README.md

[![agentmods](https://agentmods.dev/badge/instructions/mailtrap/mailtrap-mcp/claude-md/github.svg)](https://agentmods.dev/instructions/mailtrap/mailtrap-mcp/claude-md)

Your own site

<a href="https://agentmods.dev/instructions/mailtrap/mailtrap-mcp/claude-md"><img src="https://agentmods.dev/badge/instructions/mailtrap/mailtrap-mcp/claude-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.

Your own site · 80×15

<a href="https://agentmods.dev/instructions/mailtrap/mailtrap-mcp/claude-md"><img src="https://agentmods.dev/badge/instructions/mailtrap/mailtrap-mcp/claude-md.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 3,691 This file is loaded in full into every session.

When invoked 3,691 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.

Model	Per session	Once invoked
Fable 5.1	$0.03691	$0.03691
Opus 5.5	$0.01476	$0.01476
Sonnet 5.5	$0.00738	$0.00738
Haiku 4.5	$0.00369	$0.00369

Measured 3d ago against content hash cf6739fbd1cf, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

mailtrap-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 3d 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 · 238 lines

How it starts

The opening of the file, as written. The whole thing — 238 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.

Development Commands

Build and Development

npm run build - Compile TypeScript to JavaScript in the dist/ directory
npm run dev - Run the MCP server with the MCP Inspector for testing
npm run prepublishOnly - Build the project and make the executable script executable (npm publish only)

Code Quality

npm run lint - Run both ESLint and TypeScript checks
npm run lint:eslint - Run ESLint for code style checking
npm run lint:tsc - Run TypeScript compiler for type checking

Testing

npm test - Run all Jest tests
npm run test:watch - Run tests in watch mode during development
npm run test:coverage - Run tests with coverage reporting

Project Architecture

This is an MCP (Model Context Protocol) server that integrates with Mailtrap's email service. The architecture follows a modular pattern:

Core Components

src/index.ts: Main MCP server entry point that registers all tools and handles the server lifecycle
src/client.ts: Mailtrap client configuration and initialization
src/config/index.ts: Server configuration constants

Tool Architecture

All tools follow a consistent pattern in the src/tools/ directory:

Each tool (or tool group) has its own subdirectory (e.g., sendEmail/, templates/, emailLogs/)
Tools export an input schema (JSON Schema–style object for MCP inputSchema) and a handler function
Template operations are grouped under templates/ with individual files for each CRUD operation
Runtime validation: Handlers may validate input with Zod (see stats/schema.ts and getSendingStats.ts). Other tools use TypeScript types and ad-hoc checks; adding Zod validation in handlers is recommended for consistency

Tool Structure Pattern

Single-tool dirs (e.g. sendEmail/, stats/): index.ts, schema.ts (or schema.ts + Zod in handler), implementation file(s), __tests__/
Multi-tool dirs (e.g. templates/, sandbox/, emailLogs/): index.ts, schemas/*.ts (one schema per tool), implementation file(s), __tests__/

Read the full file on GitHub · 238 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.

3d ago Changed · +1 lines · +68 tokens per session cf6739fbd1cf
25d ago Changed · +1 lines · +84 tokens per session a04556d6aee7
28d ago Changed · +20 tokens per session d071ba631278
1mo ago Changed · +1 lines · +52 tokens per session a75afca9cc58
2mo ago Changed · +16 lines · +178 tokens per session a0b646787a40
2mo ago First seen · 219 lines · 3,289 tokens per session scan A 828d8f3e9cf7

Subscribe to this mod's changes

mailtrap-mcp CLAUDE.md is an instructions file published in the GitHub repository mailtrap/mailtrap-mcp (66 stars, last pushed yesterday), licensed MIT. It adds 3,691 tokens to every session, about $0.0148 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.

ai-agents bulk-email claude cursor email email-api

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mailtrap-mcp: Instructions file for Claude Code