update_webhook · Posterly MCP: Risk & Policy

WHAT IT DOES

What update_webhook does on Posterly

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

WHY IT NEEDS A POLICY

Why update_webhook needs a policy

This tool creates or modifies data (webhook configuration) reversibly. While it has outbound side effects (changing where webhook events are sent), the operation itself is not destructive—the webhook configuration can be updated again or reverted. It is Write rather than Execute because it modifies configuration data rather than triggering arbitrary code execution.

From the tool's definition Tool description explicitly states 'Update a webhook URL, events, workspace, description, or active state' and notes 'WRITE WITH OUTBOUND SIDE EFFECTS'. The tool modifies webhook configuration which controls outbound event delivery.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

update_webhook Rate-limited

update_webhook 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_webhook": {
      "limits": [
        {
          "counter": "update_webhook_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 Posterly, so you can run agents against it safely.

FAQ

Questions about update_webhook

What does the update_webhook tool do? +

Update a webhook URL, events, workspace, description, or active state. WRITE WITH OUTBOUND SIDE EFFECTS: list the current webhook first and get explicit confirmation before calling. It is categorised as a Write tool in the Posterly 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_webhook? +

Register the Posterly MCP server in PolicyLayer and add a rule for update_webhook: 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 Posterly. Nothing to install.

What risk level is update_webhook? +

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

Can I rate-limit update_webhook? +

Yes. Add a rate_limit block to the update_webhook 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_webhook completely? +

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

update_webhook is provided by the Posterly MCP server (posterly-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.