starknet_blockNumber

THE RISK

Low Risk

Why starknet_blockNumber needs a policy

This is a straightforward read-only operation that retrieves the current block number from the Starknet blockchain. It has no capacity to modify state, trigger transactions, or cause destructive changes. The blast radius of misuse is minimal—an AI agent can only retrieve this immutable chain state information.

From the tool's definition Tool name 'starknet_blockNumber' and description 'Get the most recent accepted block number' indicate a data retrieval operation with no side effects. It queries blockchain state information without modifying, deleting, or executing anything.

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

POLICY

How to control starknet_blockNumber

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

policy.json

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

starknet_blockNumber 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 Starknet 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 →

Free to start. No card required.

EXPLORE

Related tools and policies

More Starknet MCP Server tools

Read starknet_blockHashAndNumber Get the most recent accepted block hash and number Read starknet_call call a starknet function without creating a StarkNet transaction Read starknet_chainId Return the currently configured StarkNet chain id Read starknet_getBlockTransactionCount Get the number of transactions in a block given a block id Read starknet_getBlockWithReceipts Get block information with full transactions and receipts given the block id Read starknet_getBlockWithTxHashes Get block information with transaction hashes given the block id Read starknet_getBlockWithTxs Get block information with full transactions given the block id Read starknet_getClass Get the contract class definition in the given block associated with the given hash

All 21 Starknet MCP Server tools →

Read tools on other servers

M-Team MCP Server get_torrent_detail YouTube MCP Server search_channel Android Forensics ADB MCP Server parse_browser_history 0xarchive web3_challenge

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 starknet_blockNumber

What does the starknet_blockNumber tool do? +

Get the most recent accepted block number. It is categorised as a Read tool in the Starknet MCP Server MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on starknet_blockNumber? +

Register the Starknet MCP Server MCP server in PolicyLayer and add a rule for starknet_blockNumber: 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 Starknet MCP Server. Nothing to install.

What risk level is starknet_blockNumber? +

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

Can I rate-limit starknet_blockNumber? +

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

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

starknet_blockNumber is provided by the Starknet MCP Server MCP server (milancermak/starknet-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Starknet MCP Server tool call.

Start from Starknet 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 →