update_call · RetellAI MCP Server MCP: Risk & Policy

WHAT IT DOES

What update_call does on RetellAI MCP Server

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

WHY IT NEEDS A POLICY

Why update_call needs a policy

This tool modifies an existing call's properties/state in the RetellAI voice service system. Updates are categorized as Write operations since they create or modify data reversibly, unlike Destructive actions (delete) or Execute operations (which trigger external effects).

From the tool's definition Tool name is 'update_call' and description states 'Updates an existing call'. Updates are reversible modifications to existing data.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

update_call Rate-limited

update_call 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": {
    "update_call": {
      "limits": [
        {
          "counter": "update_call_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 RetellAI MCP Server, so you can run agents against it safely.

FAQ

Questions about update_call

What does the update_call tool do? +

Updates an existing call. It is categorised as a Write tool in the RetellAI MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on update_call? +

Register the RetellAI MCP Server MCP server in PolicyLayer and add a rule for update_call: 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 RetellAI MCP Server. Nothing to install.

What risk level is update_call? +

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

Can I rate-limit update_call? +

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

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

update_call is provided by the RetellAI MCP Server MCP server (kuba2290/abhaybabbar_retellai-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.