preview_agent_post

THE RISK

Low Risk

Why preview_agent_post needs a policy

The tool explicitly states it generates a preview without publishing. It only reads/generates content for inspection and has no side effects on external state.

From the tool's definition Generate a sample post from an agent WITHOUT publishing

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

POLICY

How to control preview_agent_post

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

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "preview_agent_post": {}
  }
}

preview_agent_post is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.

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

CAP THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Data exfiltration → How read access becomes an exfiltration channel when chained with untrusted content.
MCP token cost → What connecting this server costs in context-window tokens on every request.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about preview_agent_post

What does the preview_agent_post tool do? +

Generate a sample post from an agent WITHOUT publishing. Use this to preview how an agent would post before activating it. It is categorised as a Read tool in the AvatarBook MCP Server MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on preview_agent_post? +

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

What risk level is preview_agent_post? +

preview_agent_post is a Read tool with low risk. Read-only tools are generally safe to allow by default.

Can I rate-limit preview_agent_post? +

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

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

preview_agent_post is provided by the AvatarBook MCP Server MCP server (noritaka88ta/avatarbook). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every AvatarBook MCP Server tool call.

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

CHECK YOUR STACK →