holders_by_rune

THE RISK

Low Risk

Why holders_by_rune needs a policy

This tool retrieves and queries blockchain data about Rune token holders and their balances. It performs no modifications, deletions, or executable operations. The data returned is already public on the blockchain. This is a straightforward read-only query operation with minimal risk of misuse.

From the tool's definition Tool description states 'Lists all addresses currently holding a given Rune, with corresponding balances.' The verb 'lists' and the informational purpose ('visualize token distribution and adoption') indicate data retrieval with no side effects.

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

POLICY

How to control holders_by_rune

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

policy.json

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

holders_by_rune 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 Maestro 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 →

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EXPLORE

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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 →
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FAQ

Questions about holders_by_rune

What does the holders_by_rune tool do? +

Lists all addresses currently holding a given Rune, with corresponding balances. Helps visualize token distribution and adoption. It is categorised as a Read tool in the Maestro MCP Server MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on holders_by_rune? +

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

What risk level is holders_by_rune? +

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

Can I rate-limit holders_by_rune? +

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

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

holders_by_rune is provided by the Maestro MCP Server MCP server (maestro-org/maestro-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Maestro MCP Server tool call.

Start from Maestro 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 →