set_webhook

THE RISK

Medium Risk

Why set_webhook needs a policy

This tool creates or updates a webhook configuration, which is a reversible write operation (PUT). It does not move money directly, but misconfiguration could redirect payment notifications to an attacker-controlled endpoint, enabling fraud or missed payment alerts. Severity is medium due to indirect financial risk through notification hijacking.

From the tool's definition Configure a webhook URL for a given Pix key (PUT /webhook/{chave})

Documented attack patterns abuse exactly the kind of access set_webhook gives an agent:

POLICY

How to control set_webhook

PolicyLayer is an MCP gateway — it sits between your AI agents and Mcp Ap2, and nothing reaches the server without passing your rules. This is the rule we recommend for set_webhook:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "set_webhook": {
      "limits": [
        {
          "counter": "set_webhook_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

set_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.

Create a free account and register Mcp Ap2 — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

LIMIT THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

More Mcp Ap2 tools

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All 1300 Mcp Ap2 tools →

Write tools on other servers

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Argument validation → Checking tool call arguments against schema and policy before they run.
Scoped token → Per-person credentials that grant a defined subset of servers and tools.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about set_webhook

What does the set_webhook tool do? +

Configure a webhook URL for a given Pix key (PUT /webhook/{chave}). PSP will POST notifications when Pix payments arrive. It is categorised as a Write tool in the Mcp Ap2 MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on set_webhook? +

Register the Mcp Ap2 MCP server in PolicyLayer and add a rule for set_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 Mcp Ap2. Nothing to install.

What risk level is set_webhook? +

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

Can I rate-limit set_webhook? +

Yes. Add a rate_limit block to the set_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 set_webhook completely? +

Set action: deny in the PolicyLayer policy for set_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 set_webhook? +

set_webhook is provided by the Mcp Ap2 MCP server (@codespar/mcp-ap2). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Mcp Ap2 tool call.

Start from Mcp Ap2, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →