AI agents call get_block_by_hash 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 and retrieves block data from a Substrate blockchain by hash. It is a read-only operation with no side effects, no code execution capability, and no ability to modify state. The blast radius of misuse is minimal—an attacker could only retrieve existing public blockchain data, which is already globally available on the blockchain ledger.
From the tool's definition Tool name 'get_block_by_hash' and description 'Get block details by hash' indicate a retrieval operation. No modification, deletion, execution, or financial transaction is implied.
Documented attack patterns abuse exactly the kind of access get_block_by_hash 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_block_by_hash:
{
"version": "1",
"default": "deny",
"tools": {
"get_block_by_hash": {}
}
}get_block_by_hash is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Get block details by hash. 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_block_by_hash: 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_block_by_hash 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_block_by_hash 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_block_by_hash. 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_block_by_hash 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.