AI agents call topic_subscribe to retrieve information from HashPilot without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool retrieves or establishes access to message streams without creating side effects or modifying blockchain state. It is a read operation that queries or subscribes to data from an HCS (Hedera Consensus Service) topic. While it interacts with blockchain infrastructure, the operation itself is passive monitoring/subscription rather than write, execute, or destructive action.
From the tool's definition Tool subscribes to real-time messages and returns a subscription acknowledgment. Description explicitly states 'For actual message retrieval, use message_query tool', indicating this tool performs subscription management rather than data modification or…
Attacks that exploit this kind of access
Subscribe to real-time messages from an HCS topic. Returns a subscription acknowledgment. For actual message retrieval, use message_query tool to fetch historical messages. It is categorised as a Read tool in the HashPilot MCP Server, which means it retrieves data without modifying state.
Register the HashPilot MCP server in PolicyLayer and add a rule for topic_subscribe: 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 HashPilot. Nothing to install.
topic_subscribe 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 topic_subscribe 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 topic_subscribe. 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.
topic_subscribe is provided by the HashPilot MCP server (justmert/hashpilot). 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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