Shield

Name: Shield
Author: bolyra

by bolyraversion 0.1.0i★ –iRuns on your computer

Registry nameio.github.bolyra/shield

Install

Overview

Description from the maker (original English)

Stdio MCP auth proxy: wrap any MCP server with per-tool permission enforcement.

PopNx MCP’s three pillars

These three are never merged into one score: opinions, measurements and popularity are different things.

User voiceiNo reviews yetReviews open together with accounts in a later step
Our basic checksi1 of 1 passedChecked from public information; code not scanned yet
UsageiNot measured yet★ –

What you can do with it

We have not written a plain-language summary for this one yet. Below are the facts we read from the registry.

Connection: Runs on your computer
Transport: stdio
Category: Other

Install

Pick the AI app you use, then copy the settings.

Before you install

Basic checks: 1 of 1 passed
Runs on your computer with your user’s permissions (files, network, apps).
The registry lists no key to fill in.

You need

npmNode.js installed (for the npx command)

Which app do you use?

ClaudeClaude CodeCursorVS CodeChatGPT

Pick your app above. We remember it, so next time the button says “Install in …”.

Open Claude Desktop → Settings → Developer → Edit Config, and paste this into claude_desktop_config.json

{
  "mcpServers": {
    "shield": {
      "command": "npx",
      "args": [
        "-y",
        "@bolyra/shield"
      ]
    }
  }
}

Run this in your terminal

claude mcp add shield -- npx -y @bolyra/shield

Open in Cursor

Or copy the settings yourself

Paste into .cursor/mcp.json in your project, or ~/.cursor/mcp.json

{
  "mcpServers": {
    "shield": {
      "command": "npx",
      "args": [
        "-y",
        "@bolyra/shield"
      ]
    }
  }
}

Your browser asks to open the app, then the app shows the settings and asks you to confirm. Key values are left empty for you to fill in.

Open in VS Code

Or copy the settings yourself

Paste into .vscode/mcp.json in your project

{
  "servers": {
    "shield": {
      "type": "stdio",
      "command": "npx",
      "args": [
        "-y",
        "@bolyra/shield"
      ]
    }
  }
}

Your browser asks to open the app, then the app shows the settings and asks you to confirm. Key values are left empty for you to fill in.

This one runs on your computer, and ChatGPT can only connect to servers on the internet. Pick another app.

Your choice stays on this device in a cookie; no account needed.

These settings are generated from the maker’s registry entry. If the README says otherwise, follow the README.

What it can do

Runs on your computer; the tool list appears in your AI app after you install it.

Basic checksi

We check information anyone can see; we have not read the code. Checks that do not apply are left out of the count. · Checked Nov 6, 2026

✓ Pass
Maker matches the repo
The registry name was verified with the GitHub account bolyra, which owns the repo
… Not checked yet
Still maintained
We have not read this repo from GitHub yet
… Not checked yet
Has a licence
We have not read this repo from GitHub yet
– Not applicable
Endpoint responds
This one runs on your computer; there is no internet endpoint
– Not applicable
Sign-in with OAuth
Runs on your computer and uses local settings instead
… Not checked yet
No hidden instructions in tool descriptions
Runs on your computer; we can only read tool lists from internet endpoints

Compared with others in Otheri

More stars than 0% of the other 32489 servers in this category
Published to the registry more recently than 14% of the other 32489 servers in this category
Basic checks equal to or better than 100% of the other 32489 servers in this category

Compared with every active server in this category in the registry. Stars count only when the publisher owns the repo.

Common questions

Is Shield safe?

It passed 1 of 1 applicable basic checks. We have not read the code. Before adding a key or token, see what access the server asks for and use a key with only the permissions you need.

What keys or codes does it need?

The registry does not list a required key, though some servers ask you to sign in on first use.

Does it run on my computer or in the cloud?

It runs on your computer. Your AI app starts it when needed, and data does not pass through the maker’s servers (unless it calls an online service itself).

Is it still maintained?

The GitHub repo last changed –, and the latest version (0.1.0) reached the registry 5 months ago.

Which apps can use it?

Apps that support MCP, such as Claude Desktop, Claude Code, Cursor and VS Code. You also need Node.js on your computer.

What can I use instead?

In the same category: Spec Driven Development, Remote Desktop Commander, Whisper

Alternatives

Servers in the same category from other makers, sorted by stars.

Reading a card:★ GitHub starsiThree pillars: reviews · checks · usageiUpdated = latest version published to the registryi

Spec Driven Development

by formulahendry

MCP Server that facilitates spec-driven development workflows, not just Vibe Coding.

Runs on your computer★ 440MITUpdated 14 months ago

Install

Remote Desktop Commander

by desktop-commander

Remote Desktop Commander: use files, terminal and processes on your own computers from any AI app.

Runs in the cloud★ 211Updated yesterday

Install

Whisper

by whisper-sec

One routable IPv6 per AI agent, verifiable from the DNS root. Keyless tools need no signup.

Computer or cloudUpdated today

Install

README from the maker

Open the README

Copied from the maker’s repo as written. PopNx MCP has not reviewed or endorsed it. HTML, images and scripts are removed. Links lead off this site.

@bolyra/shield

Stdio MCP auth proxy. Wrap any MCP server with per-tool permission enforcement, replay protection, and audit receipts. No code changes to the server.

Quick Start

npx @bolyra/shield --server "npx @modelcontextprotocol/server-filesystem /tmp" --dev

Shield spawns the target server as a child process, intercepts tools/call requests, verifies agent credentials, and enforces tool policies before forwarding.

Config

Create shield.yaml:

devMode: true

defaultDeny: true

nonce: store: memory maxProofAge: 300

receipts: enabled: true output: stderr

tools: read_file: requireBitmask: 1 # READ_DATA write_file: requireBitmask: 2 # WRITE_DATA delete_file: requireBitmask: 2 # WRITE_DATA

Then:

npx @bolyra/shield --server "node my-server.js" --config shield.yaml

Default Deny

By default, tools without a policy entry are allowed through (only authentication is checked). Set defaultDeny: true to reject any tools/call for tool names not listed in the tools: map.

Learn Mode

Don't write the config by hand — generate a safe starting point from the server's own tool list:

npx @bolyra/shield --learn --server "node my-server.js"

Learn mode spawns the server, performs the MCP handshake (initialize → notifications/initialized → tools/list, following pagination), then writes shield.yaml (or the --config path) with:

defaultDeny: true — anything the server adds later is rejected until you allow it
every discovered tool at requireBitmask: 1 (READ_DATA) — the least-privilege floor
a _generated provenance block (source command + timestamp)

It never overwrites an existing config file, caps pagination at 50 pages, and times out after 30 seconds. The output is a starting point: review each tool and raise its requireBitmask (e.g. write_file → 2) before production use.

How It Works

Agent ←stdin/stdout→ Shield ←stdin/stdout→ MCP Server

│ verifyBundle() checkToolPolicy() nonceStore.markIfFresh() emitReceipt()

initialize, tools/list, ping — forwarded without auth
tools/call — proof extracted from params._meta.bolyra, verified, policy checked, then forwarded or rejected
Receipts emitted to stderr (stdout is the MCP transport)

Permission Bitmask

Bit	Permission
0	READ_DATA
1	WRITE_DATA
2	FINANCIAL_SMALL
3	FINANCIAL_MEDIUM
4	FINANCIAL_UNLIMITED
5	SIGN_ON_BEHALF
6	SUB_DELEGATE
7	ACCESS_PII

Shield vs Gateway

	Shield	Gateway
Transport	stdio	HTTP
Use case	Local MCP servers (Claude Desktop, Cursor)	Remote/networked MCP servers
How it wraps	Spawns child process	Reverse proxy
Proof source	`params._meta.bolyra`	`Authorization: Bolyra` header
Receipts	stderr	stdout/file/webhook

Both use the same verifyBundle() and checkToolPolicy() from @bolyra/mcp.

Library Usage

import { createShield, loadShieldConfig } from '@bolyra/shield';

const config = loadShieldConfig('./shield.yaml'); const { child, stop } = createShield(config);

Shield

Overview

PopNx MCP’s three pillars

What you can do with it

Install

Before you install

What it can do

Basic checksi

Maker matches the repo

Still maintained

Has a licence

Endpoint responds

Sign-in with OAuth

No hidden instructions in tool descriptions

Compared with others in Otheri

Common questions

Alternatives

Spec Driven Development

Remote Desktop Commander

Whisper

README from the maker

@bolyra/shield

Quick Start

Config

Default Deny

Learn Mode

How It Works

Permission Bitmask

Shield vs Gateway

Library Usage

Links