Shield vs Assay

In-depth architectural comparison of the Shield and Assay MCP servers. Compare execution transports, security boundaries, tool capabilities, quality scores, and ready-to-paste client installation snippets for Claude, Cursor, Windsurf, and VS Code.

Which MCP Server Should You Choose?

Choose Shield when:

• You need dedicated capabilities in the Security domain.
• You prefer local stdio subprocess transport architecture.
• Your security boundary fits: No auth required (Free / Open Source).
• You have access to required keys: SHIELD_CLOAK_VALUE.
• Primary tools included: Intercepts and blocks destructive tool calls with 65+ adaptive rules, Supports local stdio and remote Streamable HTTP MCP servers, TOFU pinning of tool catalogs to prevent supply-chain attacks.

Explore Shield Details

Choose Assay when:

• You need dedicated capabilities in the Security domain.
• You prefer local stdio subprocess transport architecture.
• Your security boundary fits: No auth required (Free / Open Source).
• Primary tools included: Deterministic, fail-closed policy enforcement for MCP tool calls, Offline-verifiable, tamper-evident evidence bundles of decisions and observations, Kernel-level IPv4/TCP egress enforcement via eBPF/LSM and Landlock on Linux.

Feature & Specification Comparison

Specification	Shield AperionAI Security	Assay Rul1an Security
Summary	Local guardrail proxy for AI coding agents. Wraps any MCP server (stdio or Streamable HTTP) and blocks destructive tool calls — DROP TABLE, rm -rf, force-push — before they execute. MCP supply-chain protection: TOFU tool-catalog pinning against rug pulls, plus tool-description and tool-result scanning for tool poisoning and prompt injection. 51 starter rules, approval gates, audit logging. Single binary, Apache-2.0.	Policy-as-code gate for MCP. A fail-closed proxy that denies risky tool calls before they run, produces offline-verifiable evidence bundles of what executed, and enforces IPv4/TCP egress in-kernel via eBPF/LSM and Landlock on Linux. Deterministic and offline-first.
Category & Scope

Tools & Capabilities Breakdown

Ready-to-Paste Client Configurations

Paste either (or both) of these JSON server blocks into your client config file (e.g. claude_desktop_config.json or ~/.cursor/mcp.json).

{
  "mcpServers": {
    "aperionai-shield": {
      "command": "npx",
      "args": [
        "-y",
        "@modelcontextprotocol/server-postgres"
      ],
      "env": {
        "SHIELD_CLOAK_VALUE": "YOUR_SHIELD_CLOAK_VALUE_HERE"
      }
    }
  }
}

{
  "mcpServers": {
    "rul1an-assay": {
      "command": "npx",
      "args": [
        "-y",
        "@modelcontextprotocol/server-filesystem"
      ]
    }
  }
}

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