proxy_call_tool · MCP Redirect Server MCP: Risk & Policy

WHAT IT DOES

What proxy_call_tool does on MCP Redirect Server

AI agents invoke proxy_call_tool to trigger actions in MCP Redirect Server. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.

WHY IT NEEDS A POLICY

Why proxy_call_tool needs a policy

This tool proxies tool calls to an external MCP server. Since it can invoke arbitrary tools on an external server, its effective risk depends on what tools are available there. The act of calling external tools is at minimum Execute-level, and could be Destructive or Financial depending on the proxied tool.

From the tool's definition 'Chama uma ferramenta no servidor MCP externo' (Calls a tool on the external MCP server)

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

proxy_call_tool Rate-limited

proxy_call_tool stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "proxy_call_tool": {
      "limits": [
        {
          "counter": "proxy_call_tool_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

RATE-LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches MCP Redirect Server, so you can run agents against it safely.

FAQ

Questions about proxy_call_tool

What does the proxy_call_tool tool do? +

Chama uma ferramenta no servidor MCP externo. It is categorised as a Execute tool in the MCP Redirect Server MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on proxy_call_tool? +

Register the MCP Redirect Server MCP server in PolicyLayer and add a rule for proxy_call_tool: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches MCP Redirect Server. Nothing to install.

What risk level is proxy_call_tool? +

proxy_call_tool is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit proxy_call_tool? +

Yes. Add a rate_limit block to the proxy_call_tool rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.

How do I block proxy_call_tool completely? +

Set action: deny in the PolicyLayer policy for proxy_call_tool. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.

What MCP server provides proxy_call_tool? +

proxy_call_tool is provided by the MCP Redirect Server MCP server (marcos2872/mcp-redirect-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.