getBlockNumber

THE RISK

Low Risk

Why getBlockNumber needs a policy

Getting the block number is a read-only query of public blockchain data with no side effects. The name and context (a wallet/blockchain interaction server listing methods for balance checks and contract queries) confirm this is data retrieval. Low severity because misuse poses minimal risk—an agent querying the block number cannot compromise funds, execute arbitrary code, or modify blockchain state.

From the tool's definition Tool name 'getBlockNumber' indicates retrieval of blockchain state data (current block number). No parameters or description provided suggesting write, execute, or destructive capabilities.

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 MCP Ethers Wallet, 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 MCP Ethers Wallet — 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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All 69 MCP Ethers Wallet tools →

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Go deeper

Roll out MCP under one policy → Per-person scoped tokens, one central policy, and full audit across every server your team connects.
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 →
PolicyLayer vs alternatives → How deterministic, per-call MCP policy compares with gateways, identity layers, and authorisation platforms.

FAQ

Questions about getBlockNumber

What does the getBlockNumber tool do? +

getBlockNumber. It is categorised as a Read tool in the MCP Ethers Wallet MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on getBlockNumber? +

Register the MCP Ethers Wallet 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 MCP Ethers Wallet. 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 MCP Ethers Wallet MCP server (crazyrabbitltc/mcp-ethers-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every MCP Ethers Wallet tool call.

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

CHECK YOUR STACK →