test_webhook · Posterly MCP: Risk & Policy

WHAT IT DOES

What test_webhook does on Posterly

AI agents invoke test_webhook to trigger actions in Posterly. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.

WHY IT NEEDS A POLICY

Why test_webhook needs a policy

This tool triggers an external HTTP request to a webhook URL, which is an outbound network operation with side effects on external systems. It does not merely read data, nor does it write/delete internal data — it executes an external delivery action. The description itself flags it as an 'OUTBOUND SIDE EFFECT', confirming its Execute nature.

From the tool's definition 'Send a signed webhook.test delivery to a webhook URL. OUTBOUND SIDE EFFECT: get explicit confirmation before sending a test request.'

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

test_webhook Rate-limited

test_webhook stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "test_webhook": {
      "limits": [
        {
          "counter": "test_webhook_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

RATE-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 test_webhook

What does the test_webhook tool do? +

Send a signed webhook.test delivery to a webhook URL. OUTBOUND SIDE EFFECT: get explicit confirmation before sending a test request. It is categorised as a Execute tool in the Posterly MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on test_webhook? +

Register the Posterly MCP server in PolicyLayer and add a rule for test_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 test_webhook? +

test_webhook is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit test_webhook? +

Yes. Add a rate_limit block to the test_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 test_webhook completely? +

Set action: deny in the PolicyLayer policy for test_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 test_webhook? +

test_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.