rpc_mempool_transaction_ancestors

THE RISK

Low Risk

Why rpc_mempool_transaction_ancestors needs a policy

This tool performs a read operation on blockchain data (mempool transaction ancestry information). It retrieves and queries existing data without creating, modifying, deleting, or executing any state-changing operations. The blast radius of misuse is minimal—an attacker could only enumerate transaction relationships, which is already publicly available on the blockchain.

From the tool's definition The tool 'rpc_mempool_transaction_ancestors' lists (retrieves) ancestor transactions for a given mempool transaction hash.

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

POLICY

How to control rpc_mempool_transaction_ancestors

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 rpc_mempool_transaction_ancestors:

policy.json

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

rpc_mempool_transaction_ancestors 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.

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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 rpc_mempool_transaction_ancestors

What does the rpc_mempool_transaction_ancestors tool do? +

Lists ancestor TXs for a mempool TX, by a TX hash. Useful for evaluating chains of unconfirmed transactions and replacability via Replace-By-Fee (RBF). 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 rpc_mempool_transaction_ancestors? +

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

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

Can I rate-limit rpc_mempool_transaction_ancestors? +

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

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

rpc_mempool_transaction_ancestors 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.

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