shorten_url · YOURLS- MCP: Risk & Policy

WHAT IT DOES

What shorten_url does on YOURLS-MCP

AI agents use shorten_url to create or update resources in YOURLS-MCP — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your YOURLS-MCP environment.

WHY IT NEEDS A POLICY

Why shorten_url needs a policy

This tool creates a new record (a shortened URL mapping) in the YOURLS system. It is a reversible write operation (the URL can be deleted later), with low blast radius since it only adds a URL shortening entry and does not execute code, delete data, or involve financial transactions.

From the tool's definition 'Shorten a long URL using YOURLS' — creates a new short URL entry in the YOURLS database

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

shorten_url Rate-limited

shorten_url stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "shorten_url": {
      "limits": [
        {
          "counter": "shorten_url_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL →

Instant setup, no code required.

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

FAQ

Questions about shorten_url

What does the shorten_url tool do? +

Shorten a long URL using YOURLS. It is categorised as a Write tool in the YOURLS-MCP MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on shorten_url? +

Register the YOURLS- MCP server in PolicyLayer and add a rule for shorten_url: 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 YOURLS-MCP. Nothing to install.

What risk level is shorten_url? +

shorten_url is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit shorten_url? +

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

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

shorten_url is provided by the YOURLS- MCP server (kesslerio/yourls-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.