esplora_block_header

THE RISK

Low Risk

Why esplora_block_header needs a policy

This tool retrieves blockchain metadata (block header) without creating, modifying, deleting, or executing any operations. It is a query operation that has no side effects and does not affect system state or financial assets. Low severity due to read-only nature and limited scope.

From the tool's definition Tool returns block header data via Esplora API; 'Returns the hex-encoded block header' indicates read-only data retrieval with no modification or state change

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

POLICY

How to control esplora_block_header

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 esplora_block_header:

policy.json

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

esplora_block_header 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 esplora_block_header

What does the esplora_block_header tool do? +

Returns the hex-encoded block header. 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 esplora_block_header? +

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

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

Can I rate-limit esplora_block_header? +

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

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

esplora_block_header 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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