fee_rates

THE RISK

Low Risk

Why fee_rates needs a policy

This tool queries and retrieves statistical information about Bitcoin transaction fee rates from the mempool. It performs a read operation—fetching and presenting existing blockchain data—with no capability to modify, delete, or execute transactions. The data returned is informational and publicly available on the blockchain, making it a low-severity Read operation.

From the tool's definition Tool name 'fee_rates' and description 'Statistics regarding fee rates of transactions within estimated mempool blocks' indicate retrieval of blockchain data without side effects.

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

POLICY

How to control fee_rates

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 fee_rates:

policy.json

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

fee_rates 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 →

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.
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FAQ

Questions about fee_rates

What does the fee_rates tool do? +

Statistics regarding fee rates of transactions within estimated mempool blocks. 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 fee_rates? +

Register the Maestro MCP Server MCP server in PolicyLayer and add a rule for fee_rates: 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 fee_rates? +

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

Can I rate-limit fee_rates? +

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

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

fee_rates 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 →