AI agents call list_webhooks to retrieve information from Posterly without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool retrieves configuration and status information about webhooks without creating, modifying, or deleting anything. It is a straightforward query operation with no blast radius if misused by an agent—the worst outcome would be unauthorized information disclosure about webhook configurations.
From the tool's definition Tool name 'list_webhooks' and description 'List API webhook subscriptions' — the verb 'list' indicates retrieval only.
Attacks that exploit this kind of access
List API webhook subscriptions, their event filters, active state, and most recent delivery status. It is categorised as a Read tool in the Posterly MCP Server, which means it retrieves data without modifying state.
Register the Posterly MCP server in PolicyLayer and add a rule for list_webhooks: 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.
list_webhooks is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the list_webhooks 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.
Set action: deny in the PolicyLayer policy for list_webhooks. 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.
list_webhooks 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.
Every MCP server has a record like this.
Type a name, get the same breakdown: verified identity, auth posture, risk grade, capabilities, recommended policy.
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