Check the ETH balance of an Ethereum address
AI agents call check-balance to retrieve information from MCP EVM Signer without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool retrieves balance information from a blockchain without modifying state, creating obligations, or executing arbitrary code. While the server manages private keys and can perform financial transactions (via sibling tools like send-transaction), check-balance itself is a pure read operation.
From the tool's definition Tool name 'check-balance' and description 'Check the ETH balance of an Ethereum address' indicate a query-only operation with no side effects.
Attacks that exploit this kind of access
Check the ETH balance of an Ethereum address. It is categorised as a Read tool in the MCP EVM Signer MCP Server, which means it retrieves data without modifying state.
Register the MCP EVM Signer MCP server in PolicyLayer and add a rule for check-balance: 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 EVM Signer. Nothing to install.
check-balance is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the check-balance 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.
Set action: deny in the PolicyLayer policy for check-balance. 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.
check-balance is provided by the MCP EVM Signer MCP server (zhangzhongnan928/mcp-evm-signer). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Every MCP server has a record like this.
Type a name, get the same breakdown: verified identity, auth posture, risk grade, capabilities, recommended policy.
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