proxy_request · Nango MCP: Risk & Policy

WHAT IT DOES

What proxy_request does on Nango

AI agents invoke proxy_request to trigger actions in Nango. 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_request needs a policy

This tool executes arbitrary calls to external provider APIs through a proxy. The effects depend entirely on what API endpoint and method are called - it could read data, write data, delete data, or trigger financial operations. Since the tool is a general-purpose proxy for any provider API call, it must be classified at the highest applicable severity for an Execute-type tool.

From the tool's definition 'Call a provider API through the Nango Proxy' - this executes arbitrary API calls to external provider APIs

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

proxy_request Rate-limited

proxy_request 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_request": {
      "limits": [
        {
          "counter": "proxy_request_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 Nango, so you can run agents against it safely.

FAQ

Questions about proxy_request

What does the proxy_request tool do? +

Call a provider API through the Nango Proxy without exposing provider tokens. It is categorised as a Execute tool in the Nango 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_request? +

Register the Nango MCP server in PolicyLayer and add a rule for proxy_request: 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 Nango. Nothing to install.

What risk level is proxy_request? +

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

Can I rate-limit proxy_request? +

Yes. Add a rate_limit block to the proxy_request 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_request completely? +

Set action: deny in the PolicyLayer policy for proxy_request. 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_request? +

proxy_request is provided by the Nango MCP server (levsky22/nango-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.