getBlockNumber

THE RISK

Low Risk

Why getBlockNumber needs a policy

This tool retrieves blockchain metadata (block numbers) and performs no state changes, data creation, deletion, or external operations. It is a straightforward read-only query. The low severity reflects minimal blast radius—misuse would only expose public blockchain information already available on-chain.

From the tool's definition Tool description states 'Get the current (latest) block number' - a pure query operation with no side effects. Returns data about blockchain state without modification.

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

POLICY

How to control getBlockNumber

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

policy.json

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

getBlockNumber 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 Agentek Eth — 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.
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 getBlockNumber

What does the getBlockNumber tool do? +

Get the current (latest) block number. If chainId is omitted, returns block numbers for all supported chains. It is categorised as a Read tool in the Agentek Eth MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on getBlockNumber? +

Register the Agentek Eth MCP server in PolicyLayer and add a rule for getBlockNumber: 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 Agentek Eth. Nothing to install.

What risk level is getBlockNumber? +

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

Can I rate-limit getBlockNumber? +

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

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

getBlockNumber is provided by the Agentek Eth MCP server (nanidao/agentek). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Agentek Eth tool call.

Start from Agentek Eth, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →