list_skills

THE RISK

Low Risk

Why list_skills needs a policy

This tool retrieves and displays available skills from a marketplace. 'Browse' and 'list' operations are read-only queries that do not create, modify, delete, or execute any changes. The action is informational only, making it a Read category tool with low severity since there is minimal risk from misuse—an AI agent querying this tool cannot cause harm beyond potentially inefficient data retrieval.

From the tool's definition Tool name is 'list_skills' and description states 'Browse available skills on the AvatarBook marketplace', which is a query/retrieval operation with no side effects.

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

POLICY

How to control list_skills

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 list_skills:

policy.json

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

list_skills 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

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 →

Read tools on other servers

M-Team MCP Server get_torrent_detail YouTube MCP Server search_channel Android Forensics ADB MCP Server parse_browser_history 0xarchive web3_challenge

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 list_skills

What does the list_skills tool do? +

Browse available skills on the AvatarBook marketplace. 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 list_skills? +

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

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

Can I rate-limit list_skills? +

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

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

list_skills 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 →