send_url · Viber MCP: Risk & Policy

WHAT IT DOES

What send_url does on Viber

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

WHY IT NEEDS A POLICY

Why send_url needs a policy

This tool sends messages via the Viber Bot REST API, which is a write operation that creates new message records and state changes in the Viber messaging system. While reversible (messages can be deleted), it modifies the system by adding new communications.

From the tool's definition Tool description states it 'Send[s] a URL' and 'Returns message_token for delivery tracking.' This is a message-sending operation that creates/modifies state (sending a message via the Viber Bot API).

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

send_url Rate-limited

send_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": {
    "send_url": {
      "limits": [
        {
          "counter": "send_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 Viber, so you can run agents against it safely.

FAQ

Questions about send_url

What does the send_url tool do? +

Send a URL that renders as a tappable link with preview in Viber. Use when a link is the primary content of the message. Do not use if the URL is part of longer text — embed it in send_message text instead. Returns message_token for delivery tracking. It is categorised as a Write tool in the Viber MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on send_url? +

Register the Viber MCP server in PolicyLayer and add a rule for send_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 Viber. Nothing to install.

What risk level is send_url? +

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

Can I rate-limit send_url? +

Yes. Add a rate_limit block to the send_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 send_url completely? +

Set action: deny in the PolicyLayer policy for send_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 send_url? +

send_url is provided by the Viber MCP server (serhiizghama/viber-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.