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Arc Gate MCP

by 9hannahnine-jpg

Governance proxy that filters MCP tool results for prompt injection and capability abuse using configurable policy modes.

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Install Arc Gate MCP

Pick your client, then add it in one click or paste the config.

STDIOPython
~/Library/Application Support/Claude/claude_desktop_config.json
claude_desktop_config.json
{
  "mcpServers": {
    "9hannahnine-jpg-arc-gate-mcp": {
      "command": "uvx",
      "args": [
        "arc-gate-mcp"
      ]
    }
  }
}

Settings → Developer → Edit Config, merge this into mcpServers, then fully quit and reopen Claude Desktop.

Install not yet sandbox-tested— we haven't run this command through our automated sandbox yet. Not a red flag; we're working through the catalog.

Overview

9hannahnine-jpg/arc-gate-mcp MCP server sits between an MCP client and an upstream MCP server, inspecting tool results before they reach the agent. It applies governance policies intended to block prompt injection and capability abuse at the MCP trust boundary. Choose from general-purpose, browser, finance, retrieval, or strict enforcement modes. Reach for it when an agent needs an additional runtime control layer around an existing MCP server.

Use cases

  • Proxy web-browsing tools through a browser-specific policy
  • Govern financial-data MCP results with a dedicated policy
  • Filter document-retrieval results before they reach an agent
  • Apply strict enforcement to higher-risk MCP workflows

Key features

  • MCP client-to-server governance proxy
  • Prompt injection filtering before results reach agents
  • Capability abuse prevention
  • Five named policy modes
  • Claude Desktop configuration support

Security & health

What it can reach and how reliably it runs — from our own checks, not the maintainer’s claims.

ActiveLast checked 2d ago

Recent health check succeeded.

10/10 checks healthy over the last 88d

Supply-chain signal

No high-severity advisories surfaced by our automated scan.

Critical 0High 0Medium 0Low 0

Scanned 16d ago via OSV.dev · arc-gate-mcp (PyPI)

Adoption & maintenance

Factual signals from GitHub, npm, and our automated checks — not a rating.

GitHub stars2Stargazers on the source repository.
Last commit5mo agoMost recent push to the default branch.
Directory activity5 viewsConfig copies, upvotes, and views on AllMCPs.

How Arc Gate MCP works

What 9hannahnine-jpg/arc-gate-mcp MCP server does

9hannahnine-jpg/arc-gate-mcp MCP server acts as a governance proxy for MCP tool calls. Instead of connecting an MCP client directly to an upstream server, the client connects through Arc Gate. Results returned by the upstream server pass through Arc Gate governance before they are delivered to the agent.

The stated focus is the MCP trust boundary: the proxy is designed to block prompt injection attacks delivered through tool results and to prevent capability abuse. It is therefore suited to deployments where an agent consumes data from tools that may contain untrusted or adversarial content.

How it works

Run Arc Gate with an upstream MCP server command and select a policy. The --upstream value identifies the server that Arc Gate should proxy, while --policy selects the enforcement profile. The README demonstrates an upstream Fetch server launched with uvx mcp-server-fetch.

Available policy modes are:

  • balanced for general-purpose use
  • browser_agent for web-browsing agents
  • finance_agent for financial-data agents
  • rag_assistant for document-retrieval agents
  • strict for maximum enforcement

The proxy sits in the request and response path; the documented governance behavior applies before tool results reach the agent. The material does not describe the individual detection rules, policy configuration format, or how blocked results are reported.

Setup and configuration

Install the package from PyPI with:

Terminal
pip install arc-gate-mcp

A direct launch example is:

bash
arc-gate-mcp --upstream "uvx mcp-server-fetch" --policy balanced

For Claude Desktop, the README configures the server through uvx, passing arc-gate-mcp, the upstream command, and the browser_agent policy in the MCP server definition. Replace the example upstream or policy with the values appropriate for the MCP server and agent workload you are governing.

Tools and capabilities

The primary capability is proxy-based runtime governance rather than a separate business-data tool set. Supported behavior documented for this project includes:

  • Routing an MCP client through an upstream MCP server
  • Evaluating tool results before they reach the agent
  • Applying named governance profiles
  • Using stricter enforcement for sensitive or higher-risk agent workflows
  • Running as a local command or through a Claude Desktop MCP configuration

The available policy names provide workload-oriented choices for browsing, finance, retrieval, general use, and strict enforcement. No additional MCP tools, APIs, credentials, or environment variables are documented.

Limitations and notes

The documentation does not specify whether policies can be customized, how false positives are handled, or what content is logged. It also does not list compatibility details for MCP clients other than the Claude Desktop configuration example.

The project is licensed under AGPL-3.0. The README links to Bendex Arc Platform and Heym, including a governed web research template, but those references do not document additional local configuration or authentication requirements for this package.

Read the full README View source on GitHub

Reviews

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Frequently Asked Questions about Arc Gate MCP

Run `pip install arc-gate-mcp`.

Start it with an upstream MCP command and policy, for example `arc-gate-mcp --upstream "uvx mcp-server-fetch" --policy balanced`.

Yes. The README provides a Claude Desktop configuration using `uvx` and the `arc-gate-mcp` package.

It documents `balanced`, `browser_agent`, `finance_agent`, `rag_assistant`, and `strict`.

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