open_url · Yaver MCP: Risk & Policy

WHAT IT DOES

What open_url does on Yaver

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

PARAMETERS

Parameter	Type	Required	Description
`url`	string	Yes	URL to open

Parameters from the server's own tool schema.

WHY IT NEEDS A POLICY

Why open_url needs a policy

An AI agent can call open_url faster than any human can review — one bad instruction and it creates or modifies resources in Yaver by the hundred, each call as confident as the last.

Risk signalsAccepts URL/endpoint input (url)

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

open_url Rate-limited

open_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": {
    "open_url": {
      "limits": [
        {
          "counter": "open_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 Yaver, so you can run agents against it safely.

FAQ

Questions about open_url

What does the open_url tool do? +

Open a URL in the default browser. It is categorised as a Write tool in the Yaver MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

What parameters does open_url accept? +

open_url accepts 1 parameter: url. Required: url. The full parameter table on this page comes from the server's own tool schema.

How do I enforce a policy on open_url? +

Register the Yaver MCP server in PolicyLayer and add a rule for open_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 Yaver. Nothing to install.

What risk level is open_url? +

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

Can I rate-limit open_url? +

Yes. Add a rate_limit block to the open_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 open_url completely? +

Set action: deny in the PolicyLayer policy for open_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 open_url? +

open_url is provided by the Yaver MCP server (yaver-cli). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.