list_brc20s

THE RISK

Low Risk

Why list_brc20s needs a policy

This tool only queries and returns data (BRC20 ticker information) from the Bitcoin blockchain without creating, modifying, deleting, or executing any operations. The action is informational retrieval with no ability to affect assets, transactions, or state. Severity is low because disclosure of publicly available blockchain data poses minimal direct risk.

From the tool's definition Tool name is 'list_brc20s' and description states 'Retrieves a list of tickers of all deployed BRC20 assets' — a pure read operation with no side effects.

Documented attack patterns abuse exactly the kind of access list_brc20s gives an agent:

POLICY

How to control list_brc20s

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 list_brc20s:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "list_brc20s": {}
  }
}

list_brc20s 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

Related tools and policies

More Maestro MCP Server tools

Destructive EventManagerService_DeleteTrigger Remove a trigger Deletes a specific trigger identified by its unique \ Execute esplora_broadcast_transaction Broadcast a raw transaction to the network. The transaction should be provided as hex in t Execute rpc_submit_transaction Pushes a signed raw transaction to the network. Write EventManagerService_CreateTrigger Create a new trigger Adds a trigger to a manager to listen for specific blockchain activ Write EventManagerService_UpdateTrigger Update a trigger Allows modification of a trigger Read rpc_block_range_info Fetches basic info for a contiguous block range (start and end height). Read brc20_transfer_inscriptions_by_address Returns all unspent BRC20 transfer inscriptions residing at the address. This endpoint is Read activity_by_inscription Lists all transactions that have involved the given inscription, starting from its origin

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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 list_brc20s

What does the list_brc20s tool do? +

Retrieves a list of tickers of all deployed BRC20 assets. 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 list_brc20s? +

Register the Maestro MCP Server MCP server in PolicyLayer and add a rule for list_brc20s: 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 list_brc20s? +

list_brc20s is a Read tool with low risk. Read-only tools are generally safe to allow by default.

Can I rate-limit list_brc20s? +

Yes. Add a rate_limit block to the list_brc20s 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_brc20s completely? +

Set action: deny in the PolicyLayer policy for list_brc20s. 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_brc20s? +

list_brc20s 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 →