refresh_registry · Fastmcp Gateway MCP: Risk & Policy

WHAT IT DOES

What refresh_registry does on Fastmcp Gateway

AI agents invoke refresh_registry to trigger actions in Fastmcp Gateway. 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 refresh_registry needs a policy

This tool initiates network operations against all upstream MCP servers to re-query their tool listings. It is not a simple read (it causes external side effects by opening connections and potentially altering the local registry state), nor is it destructive or financial. The closest category is Execute, as it triggers an external operation whose scope depends on how many upstream servers are configured.

From the tool's definition 'Refresh the tool registry by re-querying all upstream MCP servers' — triggers active outbound connections to multiple external servers

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

refresh_registry Rate-limited

refresh_registry 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": {
    "refresh_registry": {
      "limits": [
        {
          "counter": "refresh_registry_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 Fastmcp Gateway, so you can run agents against it safely.

FAQ

Questions about refresh_registry

What does the refresh_registry tool do? +

Refresh the tool registry by re-querying all upstream MCP servers. It is categorised as a Execute tool in the Fastmcp Gateway MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on refresh_registry? +

Register the Fastmcp Gateway MCP server in PolicyLayer and add a rule for refresh_registry: 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 Fastmcp Gateway. Nothing to install.

What risk level is refresh_registry? +

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

Can I rate-limit refresh_registry? +

Yes. Add a rate_limit block to the refresh_registry 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 refresh_registry completely? +

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

refresh_registry is provided by the Fastmcp Gateway MCP server (ultrathink-solutions/fastmcp-gateway). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.