What is mcp-proxy-wrapper CLAUDE.md?

Repository-specific engineering notes for an MCP Proxy Wrapper, a TypeScript library that places hooks around tool calls made by MCP servers. The hooks can run before or after a tool call and can change its inputs or results.

Use them when changing proxy behavior, hook interfaces, logging, tool-call interception, build commands, or tests in the MCP Proxy Wrapper repository.

They explain the library's architecture and conventions so developers can extend the wrapper without first tracing every component and hook interaction.

How mcp-plugins/mcp-proxy-wrapper configures Claude Code

Reuse

Borrowing it

Nothing to install: this file belongs to mcp-plugins/mcp-proxy-wrapper. 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/mcp-plugins/mcp-proxy-wrapper/docs/nextra-documentation/CLAUDE.md

Clone the repo

git clone --depth 1 https://github.com/mcp-plugins/mcp-proxy-wrapper

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/mcp-plugins/mcp-proxy-wrapper/claude-md/github.svg)](https://agentmods.dev/instructions/mcp-plugins/mcp-proxy-wrapper/claude-md)

Your own site

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

Per session 749 This file is loaded in full into every session.

When invoked 749 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	$0.00749	$0.00749
Opus 5.5	$0.00300	$0.00300
Sonnet 5.5	$0.00150	$0.00150
Haiku 4.5	$0.00075	$0.00075

Measured 2mo ago against content hash 5de64db4fccb, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

mcp-proxy-wrapper 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 · 89 lines

How it starts

The opening of the file, as written. The whole thing — 89 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 the MCP Proxy Wrapper - a TypeScript library that provides a hook system for intercepting and modifying tool calls in Model Context Protocol (MCP) servers. The library wraps existing MCP server instances without requiring backend infrastructure changes.

Core Architecture

Main Components

src/proxy-wrapper.ts: Core wrapper functionality that intercepts MCP server tool registrations
src/interfaces/proxy-hooks.ts: TypeScript interfaces for hooks and configuration
src/utils/logger.ts: Logging utility with configurable levels and colored output
src/index.ts: Main entry point that exports all public APIs

Hook System

The proxy wrapper implements a hook system with two main phases:

beforeToolCall: Executes before tool calls, can modify arguments or short-circuit execution
afterToolCall: Executes after tool calls, can modify results

The wrapper intercepts the server.tool() method to inject hook execution around the original tool handlers.

Development Commands

Build and Test

npm run build          # Compile TypeScript to dist/
npm test              # Run Jest test suite
npm run lint          # Run ESLint on TypeScript files
npm run format        # Format code with Prettier

Running Individual Tests

npm test -- src/proxy-wrapper.test.ts              # Run specific test file
node src/proxy-wrapper.simple.test.js              # Run JavaScript test directly

Development Workflow

npm run prepare       # Runs build automatically
npm run prepublishOnly # Runs tests and lint before publishing

Key Technical Details

Module System

Uses ES modules ("type": "module" in package.json)
TypeScript config targets ES2022 with NodeNext module resolution
Jest configured for ESM with ts-jest transform

Dependencies

Runtime: @modelcontextprotocol/sdk, zod
Development: TypeScript, Jest, ESLint, Prettier
Peer Dependencies: @modelcontextprotocol/sdk (must be provided by consuming application)

Read the full file on GitHub · 89 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.

2mo ago First seen · 89 lines · 749 tokens per session scan A 5de64db4fccb

Subscribe to this mod's changes

mcp-proxy-wrapper CLAUDE.md is an instructions file published in the GitHub repository mcp-plugins/mcp-proxy-wrapper (5 stars, last pushed 1y ago), licensed MIT. It adds 749 tokens to every session, about $0.0030 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.

Building agents

mcp-proxy-wrapper CLAUDE.md next to 6 instructions from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
mcp-proxy-wrapper CLAUDE.mdmcp-plugins/mcp-proxy-wrapper	Instructions file	5	1y ago	MIT	A	749	Claude Code
vscode buildNext.instructions.mdmicrosoft/vscode	Instructions file	195k	today	MIT	A	9,719	GitHub Copilot
vscode oss-third-party-notices.instructions.mdmicrosoft/vscode	Instructions file	195k	today	MIT	A	5,516	GitHub Copilot
next.js AGENTS.mdvercel/next.js	Instructions file	143k	yesterday	MIT	A	7,461	Codex, OpenCode
langchain AGENTS.mdlangchain-ai/langchain	Instructions file	149k	today	MIT	A	4,680	Codex, OpenCode
vscode copilot-instructions.mdmicrosoft/vscode	Instructions file	195k	today	MIT	A	3,093	GitHub Copilot
vscode model-prompts.instructions.mdmicrosoft/vscode	Instructions file	195k	today	MIT	A	2,022	GitHub Copilot

mcp-proxy-wrapper: Instructions file for Claude Code