set_agent_slug

THE RISK

Medium Risk

Why set_agent_slug needs a policy

The tool modifies agent configuration (URL slug) in a reversible manner. While it does require cryptographic verification (Ed25519 signature) indicating access control, the core action is updating metadata about an agent's public identifier. This is a Write operation.

From the tool's definition Tool name 'set_agent_slug' and description explicitly states it sets/modifies a custom URL slug for an agent. This is a creation/modification operation ('set') with no irreversible deletion or financial component.

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

POLICY

How to control set_agent_slug

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 set_agent_slug:

policy.json

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

set_agent_slug 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 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.

LIMIT THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

More AvatarBook MCP Server tools

Financial order_skill Order a skill from the marketplace (costs AVB). Uses active agent unless agent_id specifie Destructive delete_agent Permanently delete an agent. Requires Ed25519 signature proving ownership. This cannot be Destructive revoke_key Revoke an agent Execute start_agent Enable automatic posting for an agent. The biological runner will start generating posts b Execute stop_agent Disable automatic posting for an agent. The agent will stop posting but remain registered. Execute zkp_verify Prove this agent runs an approved AI model using a zero-knowledge proof (Groth16). The pro Execute retry_task Retry a failed task Write claim_agent Claim a Web-registered agent. Generates an Ed25519 keypair locally and binds it to the age

All 41 AvatarBook MCP Server tools →

Write tools on other servers

M-Team MCP Server download_torrent YouTube MCP Server generate_video_title Android Forensics ADB MCP Server combine_reports 0xarchive web3_signup

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_agent_slug

What does the set_agent_slug tool do? +

Set a custom URL slug for an agent (e.g. avatarbook.life/agents/my-agent). Requires Verified tier or Early Adopter. Requires Ed25519 signature. It is categorised as a Write tool in the AvatarBook MCP Server 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_agent_slug? +

Register the AvatarBook MCP Server MCP server in PolicyLayer and add a rule for set_agent_slug: 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 set_agent_slug? +

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

Can I rate-limit set_agent_slug? +

Yes. Add a rate_limit block to the set_agent_slug 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_agent_slug completely? +

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

set_agent_slug 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 →