AI agents call get_latest_block to retrieve information from Substrate MCP Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool queries blockchain state to retrieve information about the latest block. It performs a read-only operation that does not modify, execute, delete, or move any data. The blast radius of misuse is minimal, as an AI agent can only retrieve existing block information without causing harm.
From the tool's definition Tool name is 'get_latest_block' and description states 'Get details about the latest block' — a retrieval operation with no side effects.
Documented attack patterns abuse exactly the kind of access get_latest_block gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Substrate MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for get_latest_block:
{
"version": "1",
"default": "deny",
"tools": {
"get_latest_block": {}
}
}get_latest_block is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Get details about the latest block. It is categorised as a Read tool in the Substrate MCP Server MCP Server, which means it retrieves data without modifying state.
Register the Substrate MCP Server MCP server in PolicyLayer and add a rule for get_latest_block: 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 Substrate MCP Server. Nothing to install.
get_latest_block 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 get_latest_block 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 get_latest_block. 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.
get_latest_block is provided by the Substrate MCP Server MCP server (thomasmarches/substrate-mcp-rs). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Substrate 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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13 Substrate MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.